1.0.0[][src]Struct std::string::String

pub struct String { /* fields omitted */ }

A UTF-8 encoded, growable string.

The String type is the most common string type that has ownership over the contents of the string. It has a close relationship with its borrowed counterpart, the primitive str.

Examples

You can create a String from a literal string with String::from:

let hello = String::from("Hello, world!");Run

You can append a char to a String with the push method, and append a &str with the push_str method:

let mut hello = String::from("Hello, ");

hello.push('w');
hello.push_str("orld!");Run

If you have a vector of UTF-8 bytes, you can create a String from it with the from_utf8 method:

// some bytes, in a vector
let sparkle_heart = vec![240, 159, 146, 150];

// We know these bytes are valid, so we'll use `unwrap()`.
let sparkle_heart = String::from_utf8(sparkle_heart).unwrap();

assert_eq!("💖", sparkle_heart);Run

UTF-8

Strings are always valid UTF-8. This has a few implications, the first of which is that if you need a non-UTF-8 string, consider OsString. It is similar, but without the UTF-8 constraint. The second implication is that you cannot index into a String:

This example deliberately fails to compile
let s = "hello";

println!("The first letter of s is {}", s[0]); // ERROR!!!Run

Indexing is intended to be a constant-time operation, but UTF-8 encoding does not allow us to do this. Furthermore, it's not clear what sort of thing the index should return: a byte, a codepoint, or a grapheme cluster. The bytes and chars methods return iterators over the first two, respectively.

Deref

Strings implement Deref<Target=str>, and so inherit all of str's methods. In addition, this means that you can pass a String to a function which takes a &str by using an ampersand (&):

fn takes_str(s: &str) { }

let s = String::from("Hello");

takes_str(&s);Run

This will create a &str from the String and pass it in. This conversion is very inexpensive, and so generally, functions will accept &strs as arguments unless they need a String for some specific reason.

In certain cases Rust doesn't have enough information to make this conversion, known as Deref coercion. In the following example a string slice &'a str implements the trait TraitExample, and the function example_func takes anything that implements the trait. In this case Rust would need to make two implicit conversions, which Rust doesn't have the means to do. For that reason, the following example will not compile.

This example deliberately fails to compile
trait TraitExample {}

impl<'a> TraitExample for &'a str {}

fn example_func<A: TraitExample>(example_arg: A) {}

fn main() {
    let example_string = String::from("example_string");
    example_func(&example_string);
}Run

There are two options that would work instead. The first would be to change the line example_func(&example_string); to example_func(example_string.as_str());, using the method as_str() to explicitly extract the string slice containing the string. The second way changes example_func(&example_string); to example_func(&*example_string);. In this case we are dereferencing a String to a str, then referencing the str back to &str. The second way is more idiomatic, however both work to do the conversion explicitly rather than relying on the implicit conversion.

Representation

A String is made up of three components: a pointer to some bytes, a length, and a capacity. The pointer points to an internal buffer String uses to store its data. The length is the number of bytes currently stored in the buffer, and the capacity is the size of the buffer in bytes. As such, the length will always be less than or equal to the capacity.

This buffer is always stored on the heap.

You can look at these with the as_ptr, len, and capacity methods:

use std::mem;

let story = String::from("Once upon a time...");

let ptr = story.as_ptr();
let len = story.len();
let capacity = story.capacity();

// story has nineteen bytes
assert_eq!(19, len);

// Now that we have our parts, we throw the story away.
mem::forget(story);

// We can re-build a String out of ptr, len, and capacity. This is all
// unsafe because we are responsible for making sure the components are
// valid:
let s = unsafe { String::from_raw_parts(ptr as *mut _, len, capacity) } ;

assert_eq!(String::from("Once upon a time..."), s);Run

If a String has enough capacity, adding elements to it will not re-allocate. For example, consider this program:

let mut s = String::new();

println!("{}", s.capacity());

for _ in 0..5 {
    s.push_str("hello");
    println!("{}", s.capacity());
}Run

This will output the following:

0
5
10
20
20
40

At first, we have no memory allocated at all, but as we append to the string, it increases its capacity appropriately. If we instead use the with_capacity method to allocate the correct capacity initially:

let mut s = String::with_capacity(25);

println!("{}", s.capacity());

for _ in 0..5 {
    s.push_str("hello");
    println!("{}", s.capacity());
}Run

We end up with a different output:

25
25
25
25
25
25

Here, there's no need to allocate more memory inside the loop.

Methods

impl String[src]

pub const fn new() -> String[src]

Creates a new empty String.

Given that the String is empty, this will not allocate any initial buffer. While that means that this initial operation is very inexpensive, it may cause excessive allocation later when you add data. If you have an idea of how much data the String will hold, consider the with_capacity method to prevent excessive re-allocation.

Examples

Basic usage:

let s = String::new();Run

pub fn with_capacity(capacity: usize) -> String[src]

Creates a new empty String with a particular capacity.

Strings have an internal buffer to hold their data. The capacity is the length of that buffer, and can be queried with the capacity method. This method creates an empty String, but one with an initial buffer that can hold capacity bytes. This is useful when you may be appending a bunch of data to the String, reducing the number of reallocations it needs to do.

If the given capacity is 0, no allocation will occur, and this method is identical to the new method.

Examples

Basic usage:

let mut s = String::with_capacity(10);

// The String contains no chars, even though it has capacity for more
assert_eq!(s.len(), 0);

// These are all done without reallocating...
let cap = s.capacity();
for _ in 0..10 {
    s.push('a');
}

assert_eq!(s.capacity(), cap);

// ...but this may make the vector reallocate
s.push('a');Run

pub fn from_utf8(vec: Vec<u8>) -> Result<String, FromUtf8Error>[src]

Converts a vector of bytes to a String.

A string slice (&str) is made of bytes (u8), and a vector of bytes (Vec<u8>) is made of bytes, so this function converts between the two. Not all byte slices are valid Strings, however: String requires that it is valid UTF-8. from_utf8() checks to ensure that the bytes are valid UTF-8, and then does the conversion.

If you are sure that the byte slice is valid UTF-8, and you don't want to incur the overhead of the validity check, there is an unsafe version of this function, from_utf8_unchecked, which has the same behavior but skips the check.

This method will take care to not copy the vector, for efficiency's sake.

If you need a &str instead of a String, consider str::from_utf8.

The inverse of this method is as_bytes.

Errors

Returns Err if the slice is not UTF-8 with a description as to why the provided bytes are not UTF-8. The vector you moved in is also included.

Examples

Basic usage:

// some bytes, in a vector
let sparkle_heart = vec![240, 159, 146, 150];

// We know these bytes are valid, so we'll use `unwrap()`.
let sparkle_heart = String::from_utf8(sparkle_heart).unwrap();

assert_eq!("💖", sparkle_heart);Run

Incorrect bytes:

// some invalid bytes, in a vector
let sparkle_heart = vec![0, 159, 146, 150];

assert!(String::from_utf8(sparkle_heart).is_err());Run

See the docs for FromUtf8Error for more details on what you can do with this error.

pub fn from_utf8_lossy(v: &[u8]) -> Cow<str>[src]

Converts a slice of bytes to a string, including invalid characters.

Strings are made of bytes (u8), and a slice of bytes (&[u8]) is made of bytes, so this function converts between the two. Not all byte slices are valid strings, however: strings are required to be valid UTF-8. During this conversion, from_utf8_lossy() will replace any invalid UTF-8 sequences with U+FFFD REPLACEMENT CHARACTER, which looks like this: �

If you are sure that the byte slice is valid UTF-8, and you don't want to incur the overhead of the conversion, there is an unsafe version of this function, from_utf8_unchecked, which has the same behavior but skips the checks.

This function returns a Cow<'a, str>. If our byte slice is invalid UTF-8, then we need to insert the replacement characters, which will change the size of the string, and hence, require a String. But if it's already valid UTF-8, we don't need a new allocation. This return type allows us to handle both cases.

Examples

Basic usage:

// some bytes, in a vector
let sparkle_heart = vec![240, 159, 146, 150];

let sparkle_heart = String::from_utf8_lossy(&sparkle_heart);

assert_eq!("💖", sparkle_heart);Run

Incorrect bytes:

// some invalid bytes
let input = b"Hello \xF0\x90\x80World";
let output = String::from_utf8_lossy(input);

assert_eq!("Hello �World", output);Run

pub fn from_utf16(v: &[u16]) -> Result<String, FromUtf16Error>[src]

Decode a UTF-16 encoded vector v into a String, returning Err if v contains any invalid data.

Examples

Basic usage:

// 𝄞music
let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
          0x0073, 0x0069, 0x0063];
assert_eq!(String::from("𝄞music"),
           String::from_utf16(v).unwrap());

// 𝄞mu<invalid>ic
let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
          0xD800, 0x0069, 0x0063];
assert!(String::from_utf16(v).is_err());Run

pub fn from_utf16_lossy(v: &[u16]) -> String[src]

Decode a UTF-16 encoded slice v into a String, replacing invalid data with the replacement character (U+FFFD).

Unlike from_utf8_lossy which returns a Cow<'a, str>, from_utf16_lossy returns a String since the UTF-16 to UTF-8 conversion requires a memory allocation.

Examples

Basic usage:

// 𝄞mus<invalid>ic<invalid>
let v = &[0xD834, 0xDD1E, 0x006d, 0x0075,
          0x0073, 0xDD1E, 0x0069, 0x0063,
          0xD834];

assert_eq!(String::from("𝄞mus\u{FFFD}ic\u{FFFD}"),
           String::from_utf16_lossy(v));Run

pub unsafe fn from_raw_parts(
    buf: *mut u8,
    length: usize,
    capacity: usize
) -> String
[src]

Creates a new String from a length, capacity, and pointer.

Safety

This is highly unsafe, due to the number of invariants that aren't checked:

  • The memory at ptr needs to have been previously allocated by the same allocator the standard library uses.
  • length needs to be less than or equal to capacity.
  • capacity needs to be the correct value.

Violating these may cause problems like corrupting the allocator's internal data structures.

The ownership of ptr is effectively transferred to the String which may then deallocate, reallocate or change the contents of memory pointed to by the pointer at will. Ensure that nothing else uses the pointer after calling this function.

Examples

Basic usage:

use std::mem;

unsafe {
    let s = String::from("hello");
    let ptr = s.as_ptr();
    let len = s.len();
    let capacity = s.capacity();

    mem::forget(s);

    let s = String::from_raw_parts(ptr as *mut _, len, capacity);

    assert_eq!(String::from("hello"), s);
}Run

pub unsafe fn from_utf8_unchecked(bytes: Vec<u8>) -> String[src]

Converts a vector of bytes to a String without checking that the string contains valid UTF-8.

See the safe version, from_utf8, for more details.

Safety

This function is unsafe because it does not check that the bytes passed to it are valid UTF-8. If this constraint is violated, it may cause memory unsafety issues with future users of the String, as the rest of the standard library assumes that Strings are valid UTF-8.

Examples

Basic usage:

// some bytes, in a vector
let sparkle_heart = vec![240, 159, 146, 150];

let sparkle_heart = unsafe {
    String::from_utf8_unchecked(sparkle_heart)
};

assert_eq!("💖", sparkle_heart);Run

Important traits for Vec<u8>
pub fn into_bytes(self) -> Vec<u8>[src]

Converts a String into a byte vector.

This consumes the String, so we do not need to copy its contents.

Examples

Basic usage:

let s = String::from("hello");
let bytes = s.into_bytes();

assert_eq!(&[104, 101, 108, 108, 111][..], &bytes[..]);Run

pub fn as_str(&self) -> &str1.7.0[src]

Extracts a string slice containing the entire String.

Examples

Basic usage:

let s = String::from("foo");

assert_eq!("foo", s.as_str());Run

pub fn as_mut_str(&mut self) -> &mut str1.7.0[src]

Converts a String into a mutable string slice.

Examples

Basic usage:

let mut s = String::from("foobar");
let s_mut_str = s.as_mut_str();

s_mut_str.make_ascii_uppercase();

assert_eq!("FOOBAR", s_mut_str);Run

pub fn push_str(&mut self, string: &str)[src]

Appends a given string slice onto the end of this String.

Examples

Basic usage:

let mut s = String::from("foo");

s.push_str("bar");

assert_eq!("foobar", s);Run

pub fn capacity(&self) -> usize[src]

Returns this String's capacity, in bytes.

Examples

Basic usage:

let s = String::with_capacity(10);

assert!(s.capacity() >= 10);Run

pub fn reserve(&mut self, additional: usize)[src]

Ensures that this String's capacity is at least additional bytes larger than its length.

The capacity may be increased by more than additional bytes if it chooses, to prevent frequent reallocations.

If you do not want this "at least" behavior, see the reserve_exact method.

Panics

Panics if the new capacity overflows usize.

Examples

Basic usage:

let mut s = String::new();

s.reserve(10);

assert!(s.capacity() >= 10);Run

This may not actually increase the capacity:

let mut s = String::with_capacity(10);
s.push('a');
s.push('b');

// s now has a length of 2 and a capacity of 10
assert_eq!(2, s.len());
assert_eq!(10, s.capacity());

// Since we already have an extra 8 capacity, calling this...
s.reserve(8);

// ... doesn't actually increase.
assert_eq!(10, s.capacity());Run

pub fn reserve_exact(&mut self, additional: usize)[src]

Ensures that this String's capacity is additional bytes larger than its length.

Consider using the reserve method unless you absolutely know better than the allocator.

Panics

Panics if the new capacity overflows usize.

Examples

Basic usage:

let mut s = String::new();

s.reserve_exact(10);

assert!(s.capacity() >= 10);Run

This may not actually increase the capacity:

let mut s = String::with_capacity(10);
s.push('a');
s.push('b');

// s now has a length of 2 and a capacity of 10
assert_eq!(2, s.len());
assert_eq!(10, s.capacity());

// Since we already have an extra 8 capacity, calling this...
s.reserve_exact(8);

// ... doesn't actually increase.
assert_eq!(10, s.capacity());Run

pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError>[src]

🔬 This is a nightly-only experimental API. (try_reserve #48043)

new API

Tries to reserve capacity for at least additional more elements to be inserted in the given String. The collection may reserve more space to avoid frequent reallocations. After calling reserve, capacity will be greater than or equal to self.len() + additional. Does nothing if capacity is already sufficient.

Errors

If the capacity overflows, or the allocator reports a failure, then an error is returned.

Examples

#![feature(try_reserve)]
use std::collections::TryReserveError;

fn process_data(data: &str) -> Result<String, TryReserveError> {
    let mut output = String::new();

    // Pre-reserve the memory, exiting if we can't
    output.try_reserve(data.len())?;

    // Now we know this can't OOM in the middle of our complex work
    output.push_str(data);

    Ok(output)
}Run

pub fn try_reserve_exact(
    &mut self,
    additional: usize
) -> Result<(), TryReserveError>
[src]

🔬 This is a nightly-only experimental API. (try_reserve #48043)

new API

Tries to reserves the minimum capacity for exactly additional more elements to be inserted in the given String. After calling reserve_exact, capacity will be greater than or equal to self.len() + additional. Does nothing if the capacity is already sufficient.

Note that the allocator may give the collection more space than it requests. Therefore, capacity can not be relied upon to be precisely minimal. Prefer reserve if future insertions are expected.

Errors

If the capacity overflows, or the allocator reports a failure, then an error is returned.

Examples

#![feature(try_reserve)]
use std::collections::TryReserveError;

fn process_data(data: &str) -> Result<String, TryReserveError> {
    let mut output = String::new();

    // Pre-reserve the memory, exiting if we can't
    output.try_reserve(data.len())?;

    // Now we know this can't OOM in the middle of our complex work
    output.push_str(data);

    Ok(output)
}Run

pub fn shrink_to_fit(&mut self)[src]

Shrinks the capacity of this String to match its length.

Examples

Basic usage:

let mut s = String::from("foo");

s.reserve(100);
assert!(s.capacity() >= 100);

s.shrink_to_fit();
assert_eq!(3, s.capacity());Run

pub fn shrink_to(&mut self, min_capacity: usize)[src]

🔬 This is a nightly-only experimental API. (shrink_to #56431)

new API

Shrinks the capacity of this String with a lower bound.

The capacity will remain at least as large as both the length and the supplied value.

Panics if the current capacity is smaller than the supplied minimum capacity.

Examples

#![feature(shrink_to)]
let mut s = String::from("foo");

s.reserve(100);
assert!(s.capacity() >= 100);

s.shrink_to(10);
assert!(s.capacity() >= 10);
s.shrink_to(0);
assert!(s.capacity() >= 3);Run

pub fn push(&mut self, ch: char)[src]

Appends the given char to the end of this String.

Examples

Basic usage:

let mut s = String::from("abc");

s.push('1');
s.push('2');
s.push('3');

assert_eq!("abc123", s);Run

Important traits for &'_ [u8]
pub fn as_bytes(&self) -> &[u8][src]

Returns a byte slice of this String's contents.

The inverse of this method is from_utf8.

Examples

Basic usage:

let s = String::from("hello");

assert_eq!(&[104, 101, 108, 108, 111], s.as_bytes());Run

pub fn truncate(&mut self, new_len: usize)[src]

Shortens this String to the specified length.

If new_len is greater than the string's current length, this has no effect.

Note that this method has no effect on the allocated capacity of the string

Panics

Panics if new_len does not lie on a char boundary.

Examples

Basic usage:

let mut s = String::from("hello");

s.truncate(2);

assert_eq!("he", s);Run

pub fn pop(&mut self) -> Option<char>[src]

Removes the last character from the string buffer and returns it.

Returns None if this String is empty.

Examples

Basic usage:

let mut s = String::from("foo");

assert_eq!(s.pop(), Some('o'));
assert_eq!(s.pop(), Some('o'));
assert_eq!(s.pop(), Some('f'));

assert_eq!(s.pop(), None);Run

pub fn remove(&mut self, idx: usize) -> char[src]

Removes a char from this String at a byte position and returns it.

This is an O(n) operation, as it requires copying every element in the buffer.

Panics

Panics if idx is larger than or equal to the String's length, or if it does not lie on a char boundary.

Examples

Basic usage:

let mut s = String::from("foo");

assert_eq!(s.remove(0), 'f');
assert_eq!(s.remove(1), 'o');
assert_eq!(s.remove(0), 'o');Run

pub fn retain<F>(&mut self, f: F) where
    F: FnMut(char) -> bool
1.26.0[src]

Retains only the characters specified by the predicate.

In other words, remove all characters c such that f(c) returns false. This method operates in place, visiting each character exactly once in the original order, and preserves the order of the retained characters.

Examples

let mut s = String::from("f_o_ob_ar");

s.retain(|c| c != '_');

assert_eq!(s, "foobar");Run

The exact order may be useful for tracking external state, like an index.

let mut s = String::from("abcde");
let keep = [false, true, true, false, true];
let mut i = 0;
s.retain(|_| (keep[i], i += 1).0);
assert_eq!(s, "bce");Run

pub fn insert(&mut self, idx: usize, ch: char)[src]

Inserts a character into this String at a byte position.

This is an O(n) operation as it requires copying every element in the buffer.

Panics

Panics if idx is larger than the String's length, or if it does not lie on a char boundary.

Examples

Basic usage:

let mut s = String::with_capacity(3);

s.insert(0, 'f');
s.insert(1, 'o');
s.insert(2, 'o');

assert_eq!("foo", s);Run

pub fn insert_str(&mut self, idx: usize, string: &str)1.16.0[src]

Inserts a string slice into this String at a byte position.

This is an O(n) operation as it requires copying every element in the buffer.

Panics

Panics if idx is larger than the String's length, or if it does not lie on a char boundary.

Examples

Basic usage:

let mut s = String::from("bar");

s.insert_str(0, "foo");

assert_eq!("foobar", s);Run

Important traits for Vec<u8>
pub unsafe fn as_mut_vec(&mut self) -> &mut Vec<u8>[src]

Returns a mutable reference to the contents of this String.

Safety

This function is unsafe because it does not check that the bytes passed to it are valid UTF-8. If this constraint is violated, it may cause memory unsafety issues with future users of the String, as the rest of the standard library assumes that Strings are valid UTF-8.

Examples

Basic usage:

let mut s = String::from("hello");

unsafe {
    let vec = s.as_mut_vec();
    assert_eq!(&[104, 101, 108, 108, 111][..], &vec[..]);

    vec.reverse();
}
assert_eq!(s, "olleh");Run

pub fn len(&self) -> usize[src]

Returns the length of this String, in bytes.

Examples

Basic usage:

let a = String::from("foo");

assert_eq!(a.len(), 3);Run

pub fn is_empty(&self) -> bool[src]

Returns true if this String has a length of zero, and false otherwise.

Examples

Basic usage:

let mut v = String::new();
assert!(v.is_empty());

v.push('a');
assert!(!v.is_empty());Run

pub fn split_off(&mut self, at: usize) -> String1.16.0[src]

Splits the string into two at the given index.

Returns a newly allocated String. self contains bytes [0, at), and the returned String contains bytes [at, len). at must be on the boundary of a UTF-8 code point.

Note that the capacity of self does not change.

Panics

Panics if at is not on a UTF-8 code point boundary, or if it is beyond the last code point of the string.

Examples

let mut hello = String::from("Hello, World!");
let world = hello.split_off(7);
assert_eq!(hello, "Hello, ");
assert_eq!(world, "World!");Run

pub fn clear(&mut self)[src]

Truncates this String, removing all contents.

While this means the String will have a length of zero, it does not touch its capacity.

Examples

Basic usage:

let mut s = String::from("foo");

s.clear();

assert!(s.is_empty());
assert_eq!(0, s.len());
assert_eq!(3, s.capacity());Run

Important traits for Drain<'_>
pub fn drain<R>(&mut self, range: R) -> Drain where
    R: RangeBounds<usize>, 
1.6.0[src]

Creates a draining iterator that removes the specified range in the String and yields the removed chars.

Note: The element range is removed even if the iterator is not consumed until the end.

Panics

Panics if the starting point or end point do not lie on a char boundary, or if they're out of bounds.

Examples

Basic usage:

let mut s = String::from("α is alpha, β is beta");
let beta_offset = s.find('β').unwrap_or(s.len());

// Remove the range up until the β from the string
let t: String = s.drain(..beta_offset).collect();
assert_eq!(t, "α is alpha, ");
assert_eq!(s, "β is beta");

// A full range clears the string
s.drain(..);
assert_eq!(s, "");Run

pub fn replace_range<R>(&mut self, range: R, replace_with: &str) where
    R: RangeBounds<usize>, 
1.27.0[src]

Removes the specified range in the string, and replaces it with the given string. The given string doesn't need to be the same length as the range.

Panics

Panics if the starting point or end point do not lie on a char boundary, or if they're out of bounds.

Examples

Basic usage:

let mut s = String::from("α is alpha, β is beta");
let beta_offset = s.find('β').unwrap_or(s.len());

// Replace the range up until the β from the string
s.replace_range(..beta_offset, "Α is capital alpha; ");
assert_eq!(s, "Α is capital alpha; β is beta");Run

Important traits for Box<I>
pub fn into_boxed_str(self) -> Box<str>1.4.0[src]

Converts this String into a Box<str>.

This will drop any excess capacity.

Examples

Basic usage:

let s = String::from("hello");

let b = s.into_boxed_str();Run

Methods from Deref<Target = str>

pub const fn len(&self) -> usize[src]

Returns the length of self.

This length is in bytes, not chars or graphemes. In other words, it may not be what a human considers the length of the string.

Examples

Basic usage:

let len = "foo".len();
assert_eq!(3, len);

let len = "ƒoo".len(); // fancy f!
assert_eq!(4, len);Run

pub const fn is_empty(&self) -> bool[src]

Returns true if self has a length of zero bytes.

Examples

Basic usage:

let s = "";
assert!(s.is_empty());

let s = "not empty";
assert!(!s.is_empty());Run

pub fn is_char_boundary(&self, index: usize) -> bool1.9.0[src]

Checks that index-th byte lies at the start and/or end of a UTF-8 code point sequence.

The start and end of the string (when index == self.len()) are considered to be boundaries.

Returns false if index is greater than self.len().

Examples

let s = "Löwe 老虎 Léopard";
assert!(s.is_char_boundary(0));
// start of `老`
assert!(s.is_char_boundary(6));
assert!(s.is_char_boundary(s.len()));

// second byte of `ö`
assert!(!s.is_char_boundary(2));

// third byte of `老`
assert!(!s.is_char_boundary(8));Run

Important traits for &'_ [u8]
pub const fn as_bytes(&self) -> &[u8][src]

Converts a string slice to a byte slice. To convert the byte slice back into a string slice, use the str::from_utf8 function.

Examples

Basic usage:

let bytes = "bors".as_bytes();
assert_eq!(b"bors", bytes);Run

Important traits for &'_ [u8]
pub unsafe fn as_bytes_mut(&mut self) -> &mut [u8]1.20.0[src]

Converts a mutable string slice to a mutable byte slice. To convert the mutable byte slice back into a mutable string slice, use the str::from_utf8_mut function.

Examples

Basic usage:

let mut s = String::from("Hello");
let bytes = unsafe { s.as_bytes_mut() };

assert_eq!(b"Hello", bytes);Run

Mutability:

let mut s = String::from("🗻∈🌏");

unsafe {
    let bytes = s.as_bytes_mut();

    bytes[0] = 0xF0;
    bytes[1] = 0x9F;
    bytes[2] = 0x8D;
    bytes[3] = 0x94;
}

assert_eq!("🍔∈🌏", s);Run

pub const fn as_ptr(&self) -> *const u8[src]

Converts a string slice to a raw pointer.

As string slices are a slice of bytes, the raw pointer points to a u8. This pointer will be pointing to the first byte of the string slice.

The caller must ensure that the returned pointer is never written to. If you need to mutate the contents of the string slice, use as_mut_ptr.

Examples

Basic usage:

let s = "Hello";
let ptr = s.as_ptr();Run

pub fn as_mut_ptr(&mut self) -> *mut u81.36.0[src]

Converts a mutable string slice to a raw pointer.

As string slices are a slice of bytes, the raw pointer points to a u8. This pointer will be pointing to the first byte of the string slice.

It is your responsibility to make sure that the string slice only gets modified in a way that it remains valid UTF-8.

pub fn get<I>(&self, i: I) -> Option<&<I as SliceIndex<str>>::Output> where
    I: SliceIndex<str>, 
1.20.0[src]

Returns a subslice of str.

This is the non-panicking alternative to indexing the str. Returns None whenever equivalent indexing operation would panic.

Examples

let v = String::from("🗻∈🌏");

assert_eq!(Some("🗻"), v.get(0..4));

// indices not on UTF-8 sequence boundaries
assert!(v.get(1..).is_none());
assert!(v.get(..8).is_none());

// out of bounds
assert!(v.get(..42).is_none());Run

pub fn get_mut<I>(
    &mut self,
    i: I
) -> Option<&mut <I as SliceIndex<str>>::Output> where
    I: SliceIndex<str>, 
1.20.0[src]

Returns a mutable subslice of str.

This is the non-panicking alternative to indexing the str. Returns None whenever equivalent indexing operation would panic.

Examples

let mut v = String::from("hello");
// correct length
assert!(v.get_mut(0..5).is_some());
// out of bounds
assert!(v.get_mut(..42).is_none());
assert_eq!(Some("he"), v.get_mut(0..2).map(|v| &*v));

assert_eq!("hello", v);
{
    let s = v.get_mut(0..2);
    let s = s.map(|s| {
        s.make_ascii_uppercase();
        &*s
    });
    assert_eq!(Some("HE"), s);
}
assert_eq!("HEllo", v);Run

pub unsafe fn get_unchecked<I>(&self, i: I) -> &<I as SliceIndex<str>>::Output where
    I: SliceIndex<str>, 
1.20.0[src]

Returns a unchecked subslice of str.

This is the unchecked alternative to indexing the str.

Safety

Callers of this function are responsible that these preconditions are satisfied:

  • The starting index must come before the ending index;
  • Indexes must be within bounds of the original slice;
  • Indexes must lie on UTF-8 sequence boundaries.

Failing that, the returned string slice may reference invalid memory or violate the invariants communicated by the str type.

Examples

let v = "🗻∈🌏";
unsafe {
    assert_eq!("🗻", v.get_unchecked(0..4));
    assert_eq!("∈", v.get_unchecked(4..7));
    assert_eq!("🌏", v.get_unchecked(7..11));
}Run

pub unsafe fn get_unchecked_mut<I>(
    &mut self,
    i: I
) -> &mut <I as SliceIndex<str>>::Output where
    I: SliceIndex<str>, 
1.20.0[src]

Returns a mutable, unchecked subslice of str.

This is the unchecked alternative to indexing the str.

Safety

Callers of this function are responsible that these preconditions are satisfied:

  • The starting index must come before the ending index;
  • Indexes must be within bounds of the original slice;
  • Indexes must lie on UTF-8 sequence boundaries.

Failing that, the returned string slice may reference invalid memory or violate the invariants communicated by the str type.

Examples

let mut v = String::from("🗻∈🌏");
unsafe {
    assert_eq!("🗻", v.get_unchecked_mut(0..4));
    assert_eq!("∈", v.get_unchecked_mut(4..7));
    assert_eq!("🌏", v.get_unchecked_mut(7..11));
}Run

pub unsafe fn slice_unchecked(&self, begin: usize, end: usize) -> &str[src]

Deprecated since 1.29.0:

use get_unchecked(begin..end) instead

Creates a string slice from another string slice, bypassing safety checks.

This is generally not recommended, use with caution! For a safe alternative see str and Index.

This new slice goes from begin to end, including begin but excluding end.

To get a mutable string slice instead, see the slice_mut_unchecked method.

Safety

Callers of this function are responsible that three preconditions are satisfied:

  • begin must come before end.
  • begin and end must be byte positions within the string slice.
  • begin and end must lie on UTF-8 sequence boundaries.

Examples

Basic usage:

let s = "Löwe 老虎 Léopard";

unsafe {
    assert_eq!("Löwe 老虎 Léopard", s.slice_unchecked(0, 21));
}

let s = "Hello, world!";

unsafe {
    assert_eq!("world", s.slice_unchecked(7, 12));
}Run

pub unsafe fn slice_mut_unchecked(
    &mut self,
    begin: usize,
    end: usize
) -> &mut str
1.5.0[src]

Deprecated since 1.29.0:

use get_unchecked_mut(begin..end) instead

Creates a string slice from another string slice, bypassing safety checks. This is generally not recommended, use with caution! For a safe alternative see str and IndexMut.

This new slice goes from begin to end, including begin but excluding end.

To get an immutable string slice instead, see the slice_unchecked method.

Safety

Callers of this function are responsible that three preconditions are satisfied:

  • begin must come before end.
  • begin and end must be byte positions within the string slice.
  • begin and end must lie on UTF-8 sequence boundaries.

pub fn split_at(&self, mid: usize) -> (&str, &str)1.4.0[src]

Divide one string slice into two at an index.

The argument, mid, should be a byte offset from the start of the string. It must also be on the boundary of a UTF-8 code point.

The two slices returned go from the start of the string slice to mid, and from mid to the end of the string slice.

To get mutable string slices instead, see the split_at_mut method.

Panics

Panics if mid is not on a UTF-8 code point boundary, or if it is beyond the last code point of the string slice.

Examples

Basic usage:

let s = "Per Martin-Löf";

let (first, last) = s.split_at(3);

assert_eq!("Per", first);
assert_eq!(" Martin-Löf", last);Run

pub fn split_at_mut(&mut self, mid: usize) -> (&mut str, &mut str)1.4.0[src]

Divide one mutable string slice into two at an index.

The argument, mid, should be a byte offset from the start of the string. It must also be on the boundary of a UTF-8 code point.

The two slices returned go from the start of the string slice to mid, and from mid to the end of the string slice.

To get immutable string slices instead, see the split_at method.

Panics

Panics if mid is not on a UTF-8 code point boundary, or if it is beyond the last code point of the string slice.

Examples

Basic usage:

let mut s = "Per Martin-Löf".to_string();
{
    let (first, last) = s.split_at_mut(3);
    first.make_ascii_uppercase();
    assert_eq!("PER", first);
    assert_eq!(" Martin-Löf", last);
}
assert_eq!("PER Martin-Löf", s);Run

Important traits for Chars<'a>
pub fn chars(&self) -> Chars[src]

Returns an iterator over the chars of a string slice.

As a string slice consists of valid UTF-8, we can iterate through a string slice by char. This method returns such an iterator.

It's important to remember that char represents a Unicode Scalar Value, and may not match your idea of what a 'character' is. Iteration over grapheme clusters may be what you actually want.

Examples

Basic usage:

let word = "goodbye";

let count = word.chars().count();
assert_eq!(7, count);

let mut chars = word.chars();

assert_eq!(Some('g'), chars.next());
assert_eq!(Some('o'), chars.next());
assert_eq!(Some('o'), chars.next());
assert_eq!(Some('d'), chars.next());
assert_eq!(Some('b'), chars.next());
assert_eq!(Some('y'), chars.next());
assert_eq!(Some('e'), chars.next());

assert_eq!(None, chars.next());Run

Remember, chars may not match your human intuition about characters:

let y = "y̆";

let mut chars = y.chars();

assert_eq!(Some('y'), chars.next()); // not 'y̆'
assert_eq!(Some('\u{0306}'), chars.next());

assert_eq!(None, chars.next());Run

Important traits for CharIndices<'a>
pub fn char_indices(&self) -> CharIndices[src]

Returns an iterator over the chars of a string slice, and their positions.

As a string slice consists of valid UTF-8, we can iterate through a string slice by char. This method returns an iterator of both these chars, as well as their byte positions.

The iterator yields tuples. The position is first, the char is second.

Examples

Basic usage:

let word = "goodbye";

let count = word.char_indices().count();
assert_eq!(7, count);

let mut char_indices = word.char_indices();

assert_eq!(Some((0, 'g')), char_indices.next());
assert_eq!(Some((1, 'o')), char_indices.next());
assert_eq!(Some((2, 'o')), char_indices.next());
assert_eq!(Some((3, 'd')), char_indices.next());
assert_eq!(Some((4, 'b')), char_indices.next());
assert_eq!(Some((5, 'y')), char_indices.next());
assert_eq!(Some((6, 'e')), char_indices.next());

assert_eq!(None, char_indices.next());Run

Remember, chars may not match your human intuition about characters:

let yes = "y̆es";

let mut char_indices = yes.char_indices();

assert_eq!(Some((0, 'y')), char_indices.next()); // not (0, 'y̆')
assert_eq!(Some((1, '\u{0306}')), char_indices.next());

// note the 3 here - the last character took up two bytes
assert_eq!(Some((3, 'e')), char_indices.next());
assert_eq!(Some((4, 's')), char_indices.next());

assert_eq!(None, char_indices.next());Run

Important traits for Bytes<'_>
pub fn bytes(&self) -> Bytes[src]

An iterator over the bytes of a string slice.

As a string slice consists of a sequence of bytes, we can iterate through a string slice by byte. This method returns such an iterator.

Examples

Basic usage:

let mut bytes = "bors".bytes();

assert_eq!(Some(b'b'), bytes.next());
assert_eq!(Some(b'o'), bytes.next());
assert_eq!(Some(b'r'), bytes.next());
assert_eq!(Some(b's'), bytes.next());

assert_eq!(None, bytes.next());Run

Important traits for SplitWhitespace<'a>
pub fn split_whitespace(&self) -> SplitWhitespace1.1.0[src]

Splits a string slice by whitespace.

The iterator returned will return string slices that are sub-slices of the original string slice, separated by any amount of whitespace.

'Whitespace' is defined according to the terms of the Unicode Derived Core Property White_Space. If you only want to split on ASCII whitespace instead, use split_ascii_whitespace.

Examples

Basic usage:

let mut iter = "A few words".split_whitespace();

assert_eq!(Some("A"), iter.next());
assert_eq!(Some("few"), iter.next());
assert_eq!(Some("words"), iter.next());

assert_eq!(None, iter.next());Run

All kinds of whitespace are considered:

let mut iter = " Mary   had\ta\u{2009}little  \n\t lamb".split_whitespace();
assert_eq!(Some("Mary"), iter.next());
assert_eq!(Some("had"), iter.next());
assert_eq!(Some("a"), iter.next());
assert_eq!(Some("little"), iter.next());
assert_eq!(Some("lamb"), iter.next());

assert_eq!(None, iter.next());Run

Important traits for SplitAsciiWhitespace<'a>
pub fn split_ascii_whitespace(&self) -> SplitAsciiWhitespace1.34.0[src]

Splits a string slice by ASCII whitespace.

The iterator returned will return string slices that are sub-slices of the original string slice, separated by any amount of ASCII whitespace.

To split by Unicode Whitespace instead, use split_whitespace.

Examples

Basic usage:

let mut iter = "A few words".split_ascii_whitespace();

assert_eq!(Some("A"), iter.next());
assert_eq!(Some("few"), iter.next());
assert_eq!(Some("words"), iter.next());

assert_eq!(None, iter.next());Run

All kinds of ASCII whitespace are considered:

let mut iter = " Mary   had\ta little  \n\t lamb".split_ascii_whitespace();
assert_eq!(Some("Mary"), iter.next());
assert_eq!(Some("had"), iter.next());
assert_eq!(Some("a"), iter.next());
assert_eq!(Some("little"), iter.next());
assert_eq!(Some("lamb"), iter.next());

assert_eq!(None, iter.next());Run

Important traits for Lines<'a>
pub fn lines(&self) -> Lines[src]

An iterator over the lines of a string, as string slices.

Lines are ended with either a newline (\n) or a carriage return with a line feed (\r\n).

The final line ending is optional.

Examples

Basic usage:

let text = "foo\r\nbar\n\nbaz\n";
let mut lines = text.lines();

assert_eq!(Some("foo"), lines.next());
assert_eq!(Some("bar"), lines.next());
assert_eq!(Some(""), lines.next());
assert_eq!(Some("baz"), lines.next());

assert_eq!(None, lines.next());Run

The final line ending isn't required:

let text = "foo\nbar\n\r\nbaz";
let mut lines = text.lines();

assert_eq!(Some("foo"), lines.next());
assert_eq!(Some("bar"), lines.next());
assert_eq!(Some(""), lines.next());
assert_eq!(Some("baz"), lines.next());

assert_eq!(None, lines.next());Run

Important traits for LinesAny<'a>
pub fn lines_any(&self) -> LinesAny[src]

Deprecated since 1.4.0:

use lines() instead now

An iterator over the lines of a string.

Important traits for EncodeUtf16<'a>
pub fn encode_utf16(&self) -> EncodeUtf161.8.0[src]

Returns an iterator of u16 over the string encoded as UTF-16.

Examples

Basic usage:

let text = "Zażółć gęślą jaźń";

let utf8_len = text.len();
let utf16_len = text.encode_utf16().count();

assert!(utf16_len <= utf8_len);Run

pub fn contains<'a, P>(&'a self, pat: P) -> bool where
    P: Pattern<'a>, 
[src]

Returns true if the given pattern matches a sub-slice of this string slice.

Returns false if it does not.

Examples

Basic usage:

let bananas = "bananas";

assert!(bananas.contains("nana"));
assert!(!bananas.contains("apples"));Run

pub fn starts_with<'a, P>(&'a self, pat: P) -> bool where
    P: Pattern<'a>, 
[src]

Returns true if the given pattern matches a prefix of this string slice.

Returns false if it does not.

Examples

Basic usage:

let bananas = "bananas";

assert!(bananas.starts_with("bana"));
assert!(!bananas.starts_with("nana"));Run

pub fn ends_with<'a, P>(&'a self, pat: P) -> bool where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, 
[src]

Returns true if the given pattern matches a suffix of this string slice.

Returns false if it does not.

Examples

Basic usage:

let bananas = "bananas";

assert!(bananas.ends_with("anas"));
assert!(!bananas.ends_with("nana"));Run

pub fn find<'a, P>(&'a self, pat: P) -> Option<usize> where
    P: Pattern<'a>, 
[src]

Returns the byte index of the first character of this string slice that matches the pattern.

Returns None if the pattern doesn't match.

The pattern can be a &str, char, or a closure that determines if a character matches.

Examples

Simple patterns:

let s = "Löwe 老虎 Léopard";

assert_eq!(s.find('L'), Some(0));
assert_eq!(s.find('é'), Some(14));
assert_eq!(s.find("Léopard"), Some(13));Run

More complex patterns using point-free style and closures:

let s = "Löwe 老虎 Léopard";

assert_eq!(s.find(char::is_whitespace), Some(5));
assert_eq!(s.find(char::is_lowercase), Some(1));
assert_eq!(s.find(|c: char| c.is_whitespace() || c.is_lowercase()), Some(1));
assert_eq!(s.find(|c: char| (c < 'o') && (c > 'a')), Some(4));Run

Not finding the pattern:

let s = "Löwe 老虎 Léopard";
let x: &[_] = &['1', '2'];

assert_eq!(s.find(x), None);Run

pub fn rfind<'a, P>(&'a self, pat: P) -> Option<usize> where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, 
[src]

Returns the byte index of the last character of this string slice that matches the pattern.

Returns None if the pattern doesn't match.

The pattern can be a &str, char, or a closure that determines if a character matches.

Examples

Simple patterns:

let s = "Löwe 老虎 Léopard";

assert_eq!(s.rfind('L'), Some(13));
assert_eq!(s.rfind('é'), Some(14));Run

More complex patterns with closures:

let s = "Löwe 老虎 Léopard";

assert_eq!(s.rfind(char::is_whitespace), Some(12));
assert_eq!(s.rfind(char::is_lowercase), Some(20));Run

Not finding the pattern:

let s = "Löwe 老虎 Léopard";
let x: &[_] = &['1', '2'];

assert_eq!(s.rfind(x), None);Run

Important traits for Split<'a, P>
pub fn split<'a, P>(&'a self, pat: P) -> Split<'a, P> where
    P: Pattern<'a>, 
[src]

An iterator over substrings of this string slice, separated by characters matched by a pattern.

The pattern can be any type that implements the Pattern trait. Notable examples are &str, char, and closures that determines the split.

Iterator behavior

The returned iterator will be a DoubleEndedIterator if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, e.g., char, but not for &str.

If the pattern allows a reverse search but its results might differ from a forward search, the rsplit method can be used.

Examples

Simple patterns:

let v: Vec<&str> = "Mary had a little lamb".split(' ').collect();
assert_eq!(v, ["Mary", "had", "a", "little", "lamb"]);

let v: Vec<&str> = "".split('X').collect();
assert_eq!(v, [""]);

let v: Vec<&str> = "lionXXtigerXleopard".split('X').collect();
assert_eq!(v, ["lion", "", "tiger", "leopard"]);

let v: Vec<&str> = "lion::tiger::leopard".split("::").collect();
assert_eq!(v, ["lion", "tiger", "leopard"]);

let v: Vec<&str> = "abc1def2ghi".split(char::is_numeric).collect();
assert_eq!(v, ["abc", "def", "ghi"]);

let v: Vec<&str> = "lionXtigerXleopard".split(char::is_uppercase).collect();
assert_eq!(v, ["lion", "tiger", "leopard"]);Run

A more complex pattern, using a closure:

let v: Vec<&str> = "abc1defXghi".split(|c| c == '1' || c == 'X').collect();
assert_eq!(v, ["abc", "def", "ghi"]);Run

If a string contains multiple contiguous separators, you will end up with empty strings in the output:

let x = "||||a||b|c".to_string();
let d: Vec<_> = x.split('|').collect();

assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);Run

Contiguous separators are separated by the empty string.

let x = "(///)".to_string();
let d: Vec<_> = x.split('/').collect();

assert_eq!(d, &["(", "", "", ")"]);Run

Separators at the start or end of a string are neighbored by empty strings.

let d: Vec<_> = "010".split("0").collect();
assert_eq!(d, &["", "1", ""]);Run

When the empty string is used as a separator, it separates every character in the string, along with the beginning and end of the string.

let f: Vec<_> = "rust".split("").collect();
assert_eq!(f, &["", "r", "u", "s", "t", ""]);Run

Contiguous separators can lead to possibly surprising behavior when whitespace is used as the separator. This code is correct:

let x = "    a  b c".to_string();
let d: Vec<_> = x.split(' ').collect();

assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);Run

It does not give you:

This example is not tested
assert_eq!(d, &["a", "b", "c"]);Run

Use split_whitespace for this behavior.

Important traits for RSplit<'a, P>
pub fn rsplit<'a, P>(&'a self, pat: P) -> RSplit<'a, P> where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, 
[src]

An iterator over substrings of the given string slice, separated by characters matched by a pattern and yielded in reverse order.

The pattern can be any type that implements the Pattern trait. Notable examples are &str, char, and closures that determines the split.

Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be a DoubleEndedIterator if a forward/reverse search yields the same elements.

For iterating from the front, the split method can be used.

Examples

Simple patterns:

let v: Vec<&str> = "Mary had a little lamb".rsplit(' ').collect();
assert_eq!(v, ["lamb", "little", "a", "had", "Mary"]);

let v: Vec<&str> = "".rsplit('X').collect();
assert_eq!(v, [""]);

let v: Vec<&str> = "lionXXtigerXleopard".rsplit('X').collect();
assert_eq!(v, ["leopard", "tiger", "", "lion"]);

let v: Vec<&str> = "lion::tiger::leopard".rsplit("::").collect();
assert_eq!(v, ["leopard", "tiger", "lion"]);Run

A more complex pattern, using a closure:

let v: Vec<&str> = "abc1defXghi".rsplit(|c| c == '1' || c == 'X').collect();
assert_eq!(v, ["ghi", "def", "abc"]);Run

Important traits for SplitTerminator<'a, P>
pub fn split_terminator<'a, P>(&'a self, pat: P) -> SplitTerminator<'a, P> where
    P: Pattern<'a>, 
[src]

An iterator over substrings of the given string slice, separated by characters matched by a pattern.

The pattern can be any type that implements the Pattern trait. Notable examples are &str, char, and closures that determines the split.

Equivalent to split, except that the trailing substring is skipped if empty.

This method can be used for string data that is terminated, rather than separated by a pattern.

Iterator behavior

The returned iterator will be a DoubleEndedIterator if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, e.g., char, but not for &str.

If the pattern allows a reverse search but its results might differ from a forward search, the rsplit_terminator method can be used.

Examples

Basic usage:

let v: Vec<&str> = "A.B.".split_terminator('.').collect();
assert_eq!(v, ["A", "B"]);

let v: Vec<&str> = "A..B..".split_terminator(".").collect();
assert_eq!(v, ["A", "", "B", ""]);Run

Important traits for RSplitTerminator<'a, P>
pub fn rsplit_terminator<'a, P>(&'a self, pat: P) -> RSplitTerminator<'a, P> where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, 
[src]

An iterator over substrings of self, separated by characters matched by a pattern and yielded in reverse order.

The pattern can be any type that implements the Pattern trait. Notable examples are &str, char, and closures that determines the split. Additional libraries might provide more complex patterns like regular expressions.

Equivalent to split, except that the trailing substring is skipped if empty.

This method can be used for string data that is terminated, rather than separated by a pattern.

Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be double ended if a forward/reverse search yields the same elements.

For iterating from the front, the split_terminator method can be used.

Examples

let v: Vec<&str> = "A.B.".rsplit_terminator('.').collect();
assert_eq!(v, ["B", "A"]);

let v: Vec<&str> = "A..B..".rsplit_terminator(".").collect();
assert_eq!(v, ["", "B", "", "A"]);Run

Important traits for SplitN<'a, P>
pub fn splitn<'a, P>(&'a self, n: usize, pat: P) -> SplitN<'a, P> where
    P: Pattern<'a>, 
[src]

An iterator over substrings of the given string slice, separated by a pattern, restricted to returning at most n items.

If n substrings are returned, the last substring (the nth substring) will contain the remainder of the string.

The pattern can be any type that implements the Pattern trait. Notable examples are &str, char, and closures that determines the split.

Iterator behavior

The returned iterator will not be double ended, because it is not efficient to support.

If the pattern allows a reverse search, the rsplitn method can be used.

Examples

Simple patterns:

let v: Vec<&str> = "Mary had a little lambda".splitn(3, ' ').collect();
assert_eq!(v, ["Mary", "had", "a little lambda"]);

let v: Vec<&str> = "lionXXtigerXleopard".splitn(3, "X").collect();
assert_eq!(v, ["lion", "", "tigerXleopard"]);

let v: Vec<&str> = "abcXdef".splitn(1, 'X').collect();
assert_eq!(v, ["abcXdef"]);

let v: Vec<&str> = "".splitn(1, 'X').collect();
assert_eq!(v, [""]);Run

A more complex pattern, using a closure:

let v: Vec<&str> = "abc1defXghi".splitn(2, |c| c == '1' || c == 'X').collect();
assert_eq!(v, ["abc", "defXghi"]);Run

Important traits for RSplitN<'a, P>
pub fn rsplitn<'a, P>(&'a self, n: usize, pat: P) -> RSplitN<'a, P> where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, 
[src]

An iterator over substrings of this string slice, separated by a pattern, starting from the end of the string, restricted to returning at most n items.

If n substrings are returned, the last substring (the nth substring) will contain the remainder of the string.

The pattern can be any type that implements the Pattern trait. Notable examples are &str, char, and closures that determines the split.

Iterator behavior

The returned iterator will not be double ended, because it is not efficient to support.

For splitting from the front, the splitn method can be used.

Examples

Simple patterns:

let v: Vec<&str> = "Mary had a little lamb".rsplitn(3, ' ').collect();
assert_eq!(v, ["lamb", "little", "Mary had a"]);

let v: Vec<&str> = "lionXXtigerXleopard".rsplitn(3, 'X').collect();
assert_eq!(v, ["leopard", "tiger", "lionX"]);

let v: Vec<&str> = "lion::tiger::leopard".rsplitn(2, "::").collect();
assert_eq!(v, ["leopard", "lion::tiger"]);Run

A more complex pattern, using a closure:

let v: Vec<&str> = "abc1defXghi".rsplitn(2, |c| c == '1' || c == 'X').collect();
assert_eq!(v, ["ghi", "abc1def"]);Run

Important traits for Matches<'a, P>
pub fn matches<'a, P>(&'a self, pat: P) -> Matches<'a, P> where
    P: Pattern<'a>, 
1.2.0[src]

An iterator over the disjoint matches of a pattern within the given string slice.

The pattern can be any type that implements the Pattern trait. Notable examples are &str, char, and closures that determines the split.

Iterator behavior

The returned iterator will be a DoubleEndedIterator if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, e.g., char, but not for &str.

If the pattern allows a reverse search but its results might differ from a forward search, the rmatches method can be used.

Examples

Basic usage:

let v: Vec<&str> = "abcXXXabcYYYabc".matches("abc").collect();
assert_eq!(v, ["abc", "abc", "abc"]);

let v: Vec<&str> = "1abc2abc3".matches(char::is_numeric).collect();
assert_eq!(v, ["1", "2", "3"]);Run

Important traits for RMatches<'a, P>
pub fn rmatches<'a, P>(&'a self, pat: P) -> RMatches<'a, P> where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, 
1.2.0[src]

An iterator over the disjoint matches of a pattern within this string slice, yielded in reverse order.

The pattern can be a &str, char, or a closure that determines if a character matches.

Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be a DoubleEndedIterator if a forward/reverse search yields the same elements.

For iterating from the front, the matches method can be used.

Examples

Basic usage:

let v: Vec<&str> = "abcXXXabcYYYabc".rmatches("abc").collect();
assert_eq!(v, ["abc", "abc", "abc"]);

let v: Vec<&str> = "1abc2abc3".rmatches(char::is_numeric).collect();
assert_eq!(v, ["3", "2", "1"]);Run

Important traits for MatchIndices<'a, P>
pub fn match_indices<'a, P>(&'a self, pat: P) -> MatchIndices<'a, P> where
    P: Pattern<'a>, 
1.5.0[src]

An iterator over the disjoint matches of a pattern within this string slice as well as the index that the match starts at.

For matches of pat within self that overlap, only the indices corresponding to the first match are returned.

The pattern can be a &str, char, or a closure that determines if a character matches.

Iterator behavior

The returned iterator will be a DoubleEndedIterator if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, e.g., char, but not for &str.

If the pattern allows a reverse search but its results might differ from a forward search, the rmatch_indices method can be used.

Examples

Basic usage:

let v: Vec<_> = "abcXXXabcYYYabc".match_indices("abc").collect();
assert_eq!(v, [(0, "abc"), (6, "abc"), (12, "abc")]);

let v: Vec<_> = "1abcabc2".match_indices("abc").collect();
assert_eq!(v, [(1, "abc"), (4, "abc")]);

let v: Vec<_> = "ababa".match_indices("aba").collect();
assert_eq!(v, [(0, "aba")]); // only the first `aba`Run

Important traits for RMatchIndices<'a, P>
pub fn rmatch_indices<'a, P>(&'a self, pat: P) -> RMatchIndices<'a, P> where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, 
1.5.0[src]

An iterator over the disjoint matches of a pattern within self, yielded in reverse order along with the index of the match.

For matches of pat within self that overlap, only the indices corresponding to the last match are returned.

The pattern can be a &str, char, or a closure that determines if a character matches.

Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be a DoubleEndedIterator if a forward/reverse search yields the same elements.

For iterating from the front, the match_indices method can be used.

Examples

Basic usage:

let v: Vec<_> = "abcXXXabcYYYabc".rmatch_indices("abc").collect();
assert_eq!(v, [(12, "abc"), (6, "abc"), (0, "abc")]);

let v: Vec<_> = "1abcabc2".rmatch_indices("abc").collect();
assert_eq!(v, [(4, "abc"), (1, "abc")]);

let v: Vec<_> = "ababa".rmatch_indices("aba").collect();
assert_eq!(v, [(2, "aba")]); // only the last `aba`Run

#[must_use = "this returns the trimmed string as a slice, without modifying the original"] pub fn trim(&self) -> &str[src]

Returns a string slice with leading and trailing whitespace removed.

'Whitespace' is defined according to the terms of the Unicode Derived Core Property White_Space.

Examples

Basic usage:

let s = " Hello\tworld\t";

assert_eq!("Hello\tworld", s.trim());Run

#[must_use = "this returns the trimmed string as a new slice, without modifying the original"] pub fn trim_start(&self) -> &str1.30.0[src]

Returns a string slice with leading whitespace removed.

'Whitespace' is defined according to the terms of the Unicode Derived Core Property White_Space.

Text directionality

A string is a sequence of bytes. start in this context means the first position of that byte string; for a left-to-right language like English or Russian, this will be left side, and for right-to-left languages like Arabic or Hebrew, this will be the right side.

Examples

Basic usage:

let s = " Hello\tworld\t";
assert_eq!("Hello\tworld\t", s.trim_start());Run

Directionality:

let s = "  English  ";
assert!(Some('E') == s.trim_start().chars().next());

let s = "  עברית  ";
assert!(Some('ע') == s.trim_start().chars().next());Run

#[must_use = "this returns the trimmed string as a new slice, without modifying the original"] pub fn trim_end(&self) -> &str1.30.0[src]

Returns a string slice with trailing whitespace removed.

'Whitespace' is defined according to the terms of the Unicode Derived Core Property White_Space.

Text directionality

A string is a sequence of bytes. end in this context means the last position of that byte string; for a left-to-right language like English or Russian, this will be right side, and for right-to-left languages like Arabic or Hebrew, this will be the left side.

Examples

Basic usage:

let s = " Hello\tworld\t";
assert_eq!(" Hello\tworld", s.trim_end());Run

Directionality:

let s = "  English  ";
assert!(Some('h') == s.trim_end().chars().rev().next());

let s = "  עברית  ";
assert!(Some('ת') == s.trim_end().chars().rev().next());Run

pub fn trim_left(&self) -> &str[src]

Deprecated since 1.33.0:

superseded by trim_start

Returns a string slice with leading whitespace removed.

'Whitespace' is defined according to the terms of the Unicode Derived Core Property White_Space.

Text directionality

A string is a sequence of bytes. 'Left' in this context means the first position of that byte string; for a language like Arabic or Hebrew which are 'right to left' rather than 'left to right', this will be the right side, not the left.

Examples

Basic usage:

let s = " Hello\tworld\t";

assert_eq!("Hello\tworld\t", s.trim_left());Run

Directionality:

let s = "  English";
assert!(Some('E') == s.trim_left().chars().next());

let s = "  עברית";
assert!(Some('ע') == s.trim_left().chars().next());Run

pub fn trim_right(&self) -> &str[src]

Deprecated since 1.33.0:

superseded by trim_end

Returns a string slice with trailing whitespace removed.

'Whitespace' is defined according to the terms of the Unicode Derived Core Property White_Space.

Text directionality

A string is a sequence of bytes. 'Right' in this context means the last position of that byte string; for a language like Arabic or Hebrew which are 'right to left' rather than 'left to right', this will be the left side, not the right.

Examples

Basic usage:

let s = " Hello\tworld\t";

assert_eq!(" Hello\tworld", s.trim_right());Run

Directionality:

let s = "English  ";
assert!(Some('h') == s.trim_right().chars().rev().next());

let s = "עברית  ";
assert!(Some('ת') == s.trim_right().chars().rev().next());Run

#[must_use = "this returns the trimmed string as a new slice, without modifying the original"] pub fn trim_matches<'a, P>(&'a self, pat: P) -> &'a str where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: DoubleEndedSearcher<'a>, 
[src]

Returns a string slice with all prefixes and suffixes that match a pattern repeatedly removed.

The pattern can be a char or a closure that determines if a character matches.

Examples

Simple patterns:

assert_eq!("11foo1bar11".trim_matches('1'), "foo1bar");
assert_eq!("123foo1bar123".trim_matches(char::is_numeric), "foo1bar");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_matches(x), "foo1bar");Run

A more complex pattern, using a closure:

assert_eq!("1foo1barXX".trim_matches(|c| c == '1' || c == 'X'), "foo1bar");Run

#[must_use = "this returns the trimmed string as a new slice, without modifying the original"] pub fn trim_start_matches<'a, P>(&'a self, pat: P) -> &'a str where
    P: Pattern<'a>, 
1.30.0[src]

Returns a string slice with all prefixes that match a pattern repeatedly removed.

The pattern can be a &str, char, or a closure that determines if a character matches.

Text directionality

A string is a sequence of bytes. start in this context means the first position of that byte string; for a left-to-right language like English or Russian, this will be left side, and for right-to-left languages like Arabic or Hebrew, this will be the right side.

Examples

Basic usage:

assert_eq!("11foo1bar11".trim_start_matches('1'), "foo1bar11");
assert_eq!("123foo1bar123".trim_start_matches(char::is_numeric), "foo1bar123");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_start_matches(x), "foo1bar12");Run

#[must_use = "this returns the trimmed string as a new slice, without modifying the original"] pub fn trim_end_matches<'a, P>(&'a self, pat: P) -> &'a str where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, 
1.30.0[src]

Returns a string slice with all suffixes that match a pattern repeatedly removed.

The pattern can be a &str, char, or a closure that determines if a character matches.

Text directionality

A string is a sequence of bytes. end in this context means the last position of that byte string; for a left-to-right language like English or Russian, this will be right side, and for right-to-left languages like Arabic or Hebrew, this will be the left side.

Examples

Simple patterns:

assert_eq!("11foo1bar11".trim_end_matches('1'), "11foo1bar");
assert_eq!("123foo1bar123".trim_end_matches(char::is_numeric), "123foo1bar");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_end_matches(x), "12foo1bar");Run

A more complex pattern, using a closure:

assert_eq!("1fooX".trim_end_matches(|c| c == '1' || c == 'X'), "1foo");Run

pub fn trim_left_matches<'a, P>(&'a self, pat: P) -> &'a str where
    P: Pattern<'a>, 
[src]

Deprecated since 1.33.0:

superseded by trim_start_matches

Returns a string slice with all prefixes that match a pattern repeatedly removed.

The pattern can be a &str, char, or a closure that determines if a character matches.

Text directionality

A string is a sequence of bytes. 'Left' in this context means the first position of that byte string; for a language like Arabic or Hebrew which are 'right to left' rather than 'left to right', this will be the right side, not the left.

Examples

Basic usage:

assert_eq!("11foo1bar11".trim_left_matches('1'), "foo1bar11");
assert_eq!("123foo1bar123".trim_left_matches(char::is_numeric), "foo1bar123");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_left_matches(x), "foo1bar12");Run

pub fn trim_right_matches<'a, P>(&'a self, pat: P) -> &'a str where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>, 
[src]

Deprecated since 1.33.0:

superseded by trim_end_matches

Returns a string slice with all suffixes that match a pattern repeatedly removed.

The pattern can be a &str, char, or a closure that determines if a character matches.

Text directionality

A string is a sequence of bytes. 'Right' in this context means the last position of that byte string; for a language like Arabic or Hebrew which are 'right to left' rather than 'left to right', this will be the left side, not the right.

Examples

Simple patterns:

assert_eq!("11foo1bar11".trim_right_matches('1'), "11foo1bar");
assert_eq!("123foo1bar123".trim_right_matches(char::is_numeric), "123foo1bar");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_right_matches(x), "12foo1bar");Run

A more complex pattern, using a closure:

assert_eq!("1fooX".trim_right_matches(|c| c == '1' || c == 'X'), "1foo");Run

pub fn parse<F>(&self) -> Result<F, <F as FromStr>::Err> where
    F: FromStr
[src]

Parses this string slice into another type.

Because parse is so general, it can cause problems with type inference. As such, parse is one of the few times you'll see the syntax affectionately known as the 'turbofish': ::<>. This helps the inference algorithm understand specifically which type you're trying to parse into.

parse can parse any type that implements the FromStr trait.

Errors

Will return Err if it's not possible to parse this string slice into the desired type.

Examples

Basic usage

let four: u32 = "4".parse().unwrap();

assert_eq!(4, four);Run

Using the 'turbofish' instead of annotating four:

let four = "4".parse::<u32>();

assert_eq!(Ok(4), four);Run

Failing to parse:

let nope = "j".parse::<u32>();

assert!(nope.is_err());Run

pub fn is_ascii(&self) -> bool1.23.0[src]

Checks if all characters in this string are within the ASCII range.

Examples

let ascii = "hello!\n";
let non_ascii = "Grüße, Jürgen ❤";

assert!(ascii.is_ascii());
assert!(!non_ascii.is_ascii());Run

pub fn eq_ignore_ascii_case(&self, other: &str) -> bool1.23.0[src]

Checks that two strings are an ASCII case-insensitive match.

Same as to_ascii_lowercase(a) == to_ascii_lowercase(b), but without allocating and copying temporaries.

Examples

assert!("Ferris".eq_ignore_ascii_case("FERRIS"));
assert!("Ferrös".eq_ignore_ascii_case("FERRöS"));
assert!(!"Ferrös".eq_ignore_ascii_case("FERRÖS"));Run

pub fn make_ascii_uppercase(&mut self)1.23.0[src]

Converts this string to its ASCII upper case equivalent in-place.

ASCII letters 'a' to 'z' are mapped to 'A' to 'Z', but non-ASCII letters are unchanged.

To return a new uppercased value without modifying the existing one, use to_ascii_uppercase.

Examples

let mut s = String::from("Grüße, Jürgen ❤");

s.make_ascii_uppercase();

assert_eq!("GRüßE, JüRGEN ❤", s);Run

pub fn make_ascii_lowercase(&mut self)1.23.0[src]

Converts this string to its ASCII lower case equivalent in-place.

ASCII letters 'A' to 'Z' are mapped to 'a' to 'z', but non-ASCII letters are unchanged.

To return a new lowercased value without modifying the existing one, use to_ascii_lowercase.

Examples

let mut s = String::from("GRÜßE, JÜRGEN ❤");

s.make_ascii_lowercase();

assert_eq!("grÜße, jÜrgen ❤", s);Run

Important traits for EscapeDebug<'a>
pub fn escape_debug(&self) -> EscapeDebug1.34.0[src]

Return an iterator that escapes each char in self with char::escape_debug.

Note: only extended grapheme codepoints that begin the string will be escaped.

Examples

As an iterator:

for c in "❤\n!".escape_debug() {
    print!("{}", c);
}
println!();Run

Using println! directly:

println!("{}", "❤\n!".escape_debug());Run

Both are equivalent to:

println!("❤\\n!");Run

Using to_string:

assert_eq!("❤\n!".escape_debug().to_string(), "❤\\n!");Run

Important traits for EscapeDefault<'a>
pub fn escape_default(&self) -> EscapeDefault1.34.0[src]

Return an iterator that escapes each char in self with char::escape_default.

Examples

As an iterator:

for c in "❤\n!".escape_default() {
    print!("{}", c);
}
println!();Run

Using println! directly:

println!("{}", "❤\n!".escape_default());Run

Both are equivalent to:

println!("\\u{{2764}}\\n!");Run

Using to_string:

assert_eq!("❤\n!".escape_default().to_string(), "\\u{2764}\\n!");Run

Important traits for EscapeUnicode<'a>
pub fn escape_unicode(&self) -> EscapeUnicode1.34.0[src]

Return an iterator that escapes each char in self with char::escape_unicode.

Examples

As an iterator:

for c in "❤\n!".escape_unicode() {
    print!("{}", c);
}
println!();Run

Using println! directly:

println!("{}", "❤\n!".escape_unicode());Run

Both are equivalent to:

println!("\\u{{2764}}\\u{{a}}\\u{{21}}");Run

Using to_string:

assert_eq!("❤\n!".escape_unicode().to_string(), "\\u{2764}\\u{a}\\u{21}");Run

#[must_use = "this returns the replaced string as a new allocation, without modifying the original"] pub fn replace<'a, P>(&'a self, from: P, to: &str) -> String where
    P: Pattern<'a>, 
[src]

Replaces all matches of a pattern with another string.

replace creates a new String, and copies the data from this string slice into it. While doing so, it attempts to find matches of a pattern. If it finds any, it replaces them with the replacement string slice.

Examples

Basic usage:

let s = "this is old";

assert_eq!("this is new", s.replace("old", "new"));Run

When the pattern doesn't match:

let s = "this is old";
assert_eq!(s, s.replace("cookie monster", "little lamb"));Run

#[must_use = "this returns the replaced string as a new allocation, without modifying the original"] pub fn replacen<'a, P>(&'a self, pat: P, to: &str, count: usize) -> String where
    P: Pattern<'a>, 
1.16.0[src]

Replaces first N matches of a pattern with another string.

replacen creates a new String, and copies the data from this string slice into it. While doing so, it attempts to find matches of a pattern. If it finds any, it replaces them with the replacement string slice at most count times.

Examples

Basic usage:

let s = "foo foo 123 foo";
assert_eq!("new new 123 foo", s.replacen("foo", "new", 2));
assert_eq!("faa fao 123 foo", s.replacen('o', "a", 3));
assert_eq!("foo foo new23 foo", s.replacen(char::is_numeric, "new", 1));Run

When the pattern doesn't match:

let s = "this is old";
assert_eq!(s, s.replacen("cookie monster", "little lamb", 10));Run

pub fn to_lowercase(&self) -> String1.2.0[src]

Returns the lowercase equivalent of this string slice, as a new String.

'Lowercase' is defined according to the terms of the Unicode Derived Core Property Lowercase.

Since some characters can expand into multiple characters when changing the case, this function returns a String instead of modifying the parameter in-place.

Examples

Basic usage:

let s = "HELLO";

assert_eq!("hello", s.to_lowercase());Run

A tricky example, with sigma:

let sigma = "Σ";

assert_eq!("σ", sigma.to_lowercase());

// but at the end of a word, it's ς, not σ:
let odysseus = "ὈΔΥΣΣΕΎΣ";

assert_eq!("ὀδυσσεύς", odysseus.to_lowercase());Run

Languages without case are not changed:

let new_year = "农历新年";

assert_eq!(new_year, new_year.to_lowercase());Run

pub fn to_uppercase(&self) -> String1.2.0[src]

Returns the uppercase equivalent of this string slice, as a new String.

'Uppercase' is defined according to the terms of the Unicode Derived Core Property Uppercase.

Since some characters can expand into multiple characters when changing the case, this function returns a String instead of modifying the parameter in-place.

Examples

Basic usage:

let s = "hello";

assert_eq!("HELLO", s.to_uppercase());Run

Scripts without case are not changed:

let new_year = "农历新年";

assert_eq!(new_year, new_year.to_uppercase());Run

One character can become multiple:

let s = "tschüß";

assert_eq!("TSCHÜSS", s.to_uppercase());Run

pub fn repeat(&self, n: usize) -> String1.16.0[src]

Creates a new String by repeating a string n times.

Panics

This function will panic if the capacity would overflow.

Examples

Basic usage:

assert_eq!("abc".repeat(4), String::from("abcabcabcabc"));Run

A panic upon overflow:

fn main() {
    // this will panic at runtime
    "0123456789abcdef".repeat(usize::max_value());
}Run

pub fn to_ascii_uppercase(&self) -> String1.23.0[src]

Returns a copy of this string where each character is mapped to its ASCII upper case equivalent.

ASCII letters 'a' to 'z' are mapped to 'A' to 'Z', but non-ASCII letters are unchanged.

To uppercase the value in-place, use make_ascii_uppercase.

To uppercase ASCII characters in addition to non-ASCII characters, use to_uppercase.

Examples

let s = "Grüße, Jürgen ❤";

assert_eq!("GRüßE, JüRGEN ❤", s.to_ascii_uppercase());Run

pub fn to_ascii_lowercase(&self) -> String1.23.0[src]

Returns a copy of this string where each character is mapped to its ASCII lower case equivalent.

ASCII letters 'A' to 'Z' are mapped to 'a' to 'z', but non-ASCII letters are unchanged.

To lowercase the value in-place, use make_ascii_lowercase.

To lowercase ASCII characters in addition to non-ASCII characters, use to_lowercase.

Examples

let s = "Grüße, Jürgen ❤";

assert_eq!("grüße, jürgen ❤", s.to_ascii_lowercase());Run

Trait Implementations

impl FromStr for String[src]

type Err = Infallible

The associated error which can be returned from parsing.

impl Eq for String[src]

impl Deref for String[src]

type Target = str

The resulting type after dereferencing.

impl From<String> for Rc<str>1.21.0[src]

impl From<String> for Arc<str>1.21.0[src]

impl<'_> From<&'_ String> for String1.35.0[src]

impl<'a> From<Cow<'a, str>> for String1.14.0[src]

impl<'a> From<String> for Cow<'a, str>[src]

impl From<String> for Vec<u8>1.14.0[src]

Important traits for Vec<u8>
fn from(string: String) -> Vec<u8>[src]

Converts the given String to a vector Vec that holds values of type u8.

Examples

Basic usage:

let s1 = String::from("hello world");
let v1 = Vec::from(s1);

for b in v1 {
    println!("{}", b);
}Run

impl<'_> From<&'_ str> for String[src]

impl From<String> for Box<str>1.20.0[src]

Important traits for Box<I>
fn from(s: String) -> Box<str>[src]

Converts the given String to a boxed str slice that is owned.

Examples

Basic usage:

let s1: String = String::from("hello world");
let s2: Box<str> = Box::from(s1);
let s3: String = String::from(s2);

assert_eq!("hello world", s3)Run

impl<'a> From<&'a String> for Cow<'a, str>1.28.0[src]

impl From<Box<str>> for String1.18.0[src]

fn from(s: Box<str>) -> String[src]

Converts the given boxed str slice to a String. It is notable that the str slice is owned.

Examples

Basic usage:

let s1: String = String::from("hello world");
let s2: Box<str> = s1.into_boxed_str();
let s3: String = String::from(s2);

assert_eq!("hello world", s3)Run

impl Hash for String[src]

impl<'a, 'b> PartialEq<String> for Cow<'a, str>[src]

impl<'a, 'b> PartialEq<String> for &'a str[src]

impl<'a, 'b> PartialEq<String> for str[src]

impl<'a, 'b> PartialEq<str> for String[src]

impl<'a, 'b> PartialEq<&'a str> for String[src]

impl<'a, 'b> PartialEq<Cow<'a, str>> for String[src]

impl PartialEq<String> for String[src]

impl IndexMut<RangeFull> for String1.3.0[src]

impl IndexMut<Range<usize>> for String1.3.0[src]

impl IndexMut<RangeToInclusive<usize>> for String1.26.0[src]

impl IndexMut<RangeTo<usize>> for String1.3.0[src]

impl IndexMut<RangeFrom<usize>> for String1.3.0[src]

impl IndexMut<RangeInclusive<usize>> for String1.26.0[src]

impl AsRef<str> for String[src]

impl AsRef<[u8]> for String[src]

impl<'_> AddAssign<&'_ str> for String1.12.0[src]

Implements the += operator for appending to a String.

This has the same behavior as the push_str method.

impl<'a> FromIterator<String> for Cow<'a, str>1.12.0[src]

impl FromIterator<String> for String1.4.0[src]

impl<'a> FromIterator<&'a str> for String[src]

impl<'a> FromIterator<Cow<'a, str>> for String1.19.0[src]

impl<'a> FromIterator<&'a char> for String1.17.0[src]

impl FromIterator<char> for String[src]

impl<'a, 'b> Pattern<'a> for &'b String[src]

A convenience impl that delegates to the impl for &str

type Searcher = <&'b str as Pattern<'a>>::Searcher

🔬 This is a nightly-only experimental API. (pattern #27721)

API not fully fleshed out and ready to be stabilized

Associated searcher for this pattern

impl Index<RangeFull> for String[src]

type Output = str

The returned type after indexing.

impl Index<RangeFrom<usize>> for String[src]

type Output = str

The returned type after indexing.

impl Index<RangeInclusive<usize>> for String1.26.0[src]

type Output = str

The returned type after indexing.

impl Index<RangeToInclusive<usize>> for String1.26.0[src]

type Output = str

The returned type after indexing.

impl Index<Range<usize>> for String[src]

type Output = str

The returned type after indexing.

impl Index<RangeTo<usize>> for String[src]

type Output = str

The returned type after indexing.

impl Display for String[src]

impl Borrow<str> for String[src]

impl Ord for String[src]

impl Clone for String[src]

impl BorrowMut<str> for String1.36.0[src]

impl Debug for String[src]

impl ToString for String1.17.0[src]

impl<'_> Add<&'_ str> for String[src]

Implements the + operator for concatenating two strings.

This consumes the String on the left-hand side and re-uses its buffer (growing it if necessary). This is done to avoid allocating a new String and copying the entire contents on every operation, which would lead to O(n^2) running time when building an n-byte string by repeated concatenation.

The string on the right-hand side is only borrowed; its contents are copied into the returned String.

Examples

Concatenating two Strings takes the first by value and borrows the second:

let a = String::from("hello");
let b = String::from(" world");
let c = a + &b;
// `a` is moved and can no longer be used here.Run

If you want to keep using the first String, you can clone it and append to the clone instead:

let a = String::from("hello");
let b = String::from(" world");
let c = a.clone() + &b;
// `a` is still valid here.Run

Concatenating &str slices can be done by converting the first to a String:

let a = "hello";
let b = " world";
let c = a.to_string() + b;Run

type Output = String

The resulting type after applying the + operator.

impl PartialOrd<String> for String[src]

impl Default for String[src]

fn default() -> String[src]

Creates an empty String.

impl Write for String[src]

impl DerefMut for String1.3.0[src]

impl Extend<char> for String[src]

impl<'a> Extend<&'a str> for String[src]

impl Extend<String> for String1.4.0[src]

impl<'a> Extend<&'a char> for String1.2.0[src]

impl<'a> Extend<Cow<'a, str>> for String1.19.0[src]

impl ToSocketAddrs for String1.16.0[src]

type Iter = IntoIter<SocketAddr>

Returned iterator over socket addresses which this type may correspond to. Read more

impl From<String> for Box<dyn Error + Send + Sync>[src]

Important traits for Box<I>
fn from(err: String) -> Box<dyn Error + Send + Sync>[src]

Converts a String into a box of dyn Error + trait@Send + trait@Sync.

Examples

use std::error::Error;
use std::mem;

let a_string_error = "a string error".to_string();
let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_string_error);
assert!(
    mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))Run

impl From<String> for Box<dyn Error>1.6.0[src]

Important traits for Box<I>
fn from(str_err: String) -> Box<dyn Error>[src]

Converts a String into a box of dyn Error.

Examples

use std::error::Error;
use std::mem;

let a_string_error = "a string error".to_string();
let a_boxed_error = Box::<dyn Error>::from(a_string_error);
assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))Run

impl From<String> for OsString[src]

fn from(s: String) -> OsString[src]

Converts a String into a OsString.

The conversion copies the data, and includes an allocation on the heap.

impl From<String> for PathBuf[src]

fn from(s: String) -> PathBuf[src]

Converts a String into a PathBuf

This conversion does not allocate or copy memory.

impl AsRef<OsStr> for String[src]

impl AsRef<Path> for String[src]

Auto Trait Implementations

impl UnwindSafe for String

impl RefUnwindSafe for String

impl Unpin for String

impl Send for String

impl Sync for String

Blanket Implementations

impl<T> From<T> for T[src]

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 
[src]

type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> Into<U> for T where
    U: From<T>, 
[src]

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 
[src]

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

impl<T> Borrow<T> for T where
    T: ?Sized
[src]

impl<T> BorrowMut<T> for T where
    T: ?Sized
[src]

impl<T> Any for T where
    T: 'static + ?Sized
[src]

impl<T> ToOwned for T where
    T: Clone
[src]

type Owned = T

The resulting type after obtaining ownership.

impl<T> ToString for T where
    T: Display + ?Sized
[src]