1.2.0[−][src]Struct alloc::fmt::DebugMap
A struct to help with fmt::Debug
implementations.
This is useful when you wish to output a formatted map as a part of your
Debug::fmt
implementation.
This can be constructed by the
Formatter::debug_map
method.
Examples
use std::fmt; struct Foo(Vec<(String, i32)>); impl fmt::Debug for Foo { fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result { fmt.debug_map().entries(self.0.iter().map(|&(ref k, ref v)| (k, v))).finish() } } assert_eq!( format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])), "{\"A\": 10, \"B\": 11}", );
Methods
impl<'a, 'b> DebugMap<'a, 'b> where
'b: 'a,
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'b: 'a,
pub fn entry(
&mut self,
key: &dyn Debug,
value: &dyn Debug
) -> &mut DebugMap<'a, 'b>
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&mut self,
key: &dyn Debug,
value: &dyn Debug
) -> &mut DebugMap<'a, 'b>
Adds a new entry to the map output.
Examples
use std::fmt; struct Foo(Vec<(String, i32)>); impl fmt::Debug for Foo { fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { fmt.debug_map() .entry(&"whole", &self.0) // We add the "whole" entry. .finish() } } assert_eq!( format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])), "{\"whole\": [(\"A\", 10), (\"B\", 11)]}", );
pub fn key(&mut self, key: &dyn Debug) -> &mut DebugMap<'a, 'b>
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🔬 This is a nightly-only experimental API. (debug_map_key_value
#62482)
recently added
Adds the key part of a new entry to the map output.
This method, together with value
, is an alternative to entry
that
can be used when the complete entry isn't known upfront. Prefer the entry
method when it's possible to use.
Panics
key
must be called before value
and each call to key
must be followed
by a corresponding call to value
. Otherwise this method will panic.
Examples
use std::fmt; struct Foo(Vec<(String, i32)>); impl fmt::Debug for Foo { fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { fmt.debug_map() .key(&"whole").value(&self.0) // We add the "whole" entry. .finish() } } assert_eq!( format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])), "{\"whole\": [(\"A\", 10), (\"B\", 11)]}", );
pub fn value(&mut self, value: &dyn Debug) -> &mut DebugMap<'a, 'b>
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🔬 This is a nightly-only experimental API. (debug_map_key_value
#62482)
recently added
Adds the value part of a new entry to the map output.
This method, together with key
, is an alternative to entry
that
can be used when the complete entry isn't known upfront. Prefer the entry
method when it's possible to use.
Panics
key
must be called before value
and each call to key
must be followed
by a corresponding call to value
. Otherwise this method will panic.
Examples
use std::fmt; struct Foo(Vec<(String, i32)>); impl fmt::Debug for Foo { fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { fmt.debug_map() .key(&"whole").value(&self.0) // We add the "whole" entry. .finish() } } assert_eq!( format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])), "{\"whole\": [(\"A\", 10), (\"B\", 11)]}", );
pub fn entries<K, V, I>(&mut self, entries: I) -> &mut DebugMap<'a, 'b> where
I: IntoIterator<Item = (K, V)>,
K: Debug,
V: Debug,
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I: IntoIterator<Item = (K, V)>,
K: Debug,
V: Debug,
Adds the contents of an iterator of entries to the map output.
Examples
use std::fmt; struct Foo(Vec<(String, i32)>); impl fmt::Debug for Foo { fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { fmt.debug_map() // We map our vec so each entries' first field will become // the "key". .entries(self.0.iter().map(|&(ref k, ref v)| (k, v))) .finish() } } assert_eq!( format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])), "{\"A\": 10, \"B\": 11}", );
pub fn finish(&mut self) -> Result<(), Error>
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Finishes output and returns any error encountered.
Panics
key
must be called before value
and each call to key
must be followed
by a corresponding call to value
. Otherwise this method will panic.
Examples
use std::fmt; struct Foo(Vec<(String, i32)>); impl fmt::Debug for Foo { fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { fmt.debug_map() .entries(self.0.iter().map(|&(ref k, ref v)| (k, v))) .finish() // Ends the struct formatting. } } assert_eq!( format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])), "{\"A\": 10, \"B\": 11}", );
Auto Trait Implementations
impl<'a, 'b> Unpin for DebugMap<'a, 'b> where
'b: 'a,
'b: 'a,
impl<'a, 'b> !Send for DebugMap<'a, 'b>
impl<'a, 'b> !Sync for DebugMap<'a, 'b>
Blanket Implementations
impl<T> From<T> for T
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impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
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impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
fn borrow_mut(&mut self) -> &mut T
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impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,