Trait std::convert::AsMut

pub trait AsMut<T> where
    T: ?Sized, {
    fn as_mut(&mut self) -> &mut T;
}

Used to do a cheap mutable-to-mutable reference conversion.

This trait is similar to AsRef but used for converting between mutable references. If you need to do a costly conversion it is better to implement From with type &mut T or write a custom function.

Note: This trait must not fail. If the conversion can fail, use a dedicated method which returns an Option<T> or a Result<T, E>.

Generic Implementations

• AsMut auto-dereferences if the inner type is a mutable reference (e.g.: foo.as_mut() will work the same if foo has type &mut Foo or &mut &mut Foo)

Examples

Using AsMut as trait bound for a generic function we can accept all mutable references that can be converted to type &mut T. Because Box<T> implements AsMut<T> we can write a function add_one that takes all arguments that can be converted to &mut u64. Because Box<T> implements AsMut<T>, add_one accepts arguments of type &mut Box<u64> as well:

fn add_one<T: AsMut<u64>>(num: &mut T) {
    *num.as_mut() += 1;
}

let mut boxed_num = Box::new(0);
add_one(&mut boxed_num);
assert_eq!(*boxed_num, 1);

Required methods

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W

fn as_mut(&mut self) -> &mut T

Performs the conversion.

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Implementors

impl<'_, T, U> AsMut<U> for &'_ mut T where
    T: AsMut<U> + ?Sized,
    U: ?Sized, 

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W

fn as_mut(&mut self) -> &mut U

impl<T> AsMut<[T]> for [T]

Important traits for &'_ [u8]

impl<'_> Read for &'_ [u8]impl<'_> Write for &'_ mut [u8]

fn as_mut(&mut self) -> &mut [T]

impl<T> AsMut<[T]> for Vec<T>

Important traits for &'_ [u8]

impl<'_> Read for &'_ [u8]impl<'_> Write for &'_ mut [u8]

fn as_mut(&mut self) -> &mut [T]

impl<T> AsMut<Vec<T>> for Vec<T>

Important traits for Vec<u8>

impl Write for Vec<u8>

fn as_mut(&mut self) -> &mut Vec<T>

impl<T> AsMut<T> for Box<T> where
    T: ?Sized, 

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, R: Read + ?Sized> Read for &'_ mut Rimpl<'_, W: Write + ?Sized> Write for &'_ mut W

fn as_mut(&mut self) -> &mut T

impl<const N: usize, T> AsMut<[T]> for [T; N] where
    [T; N]: LengthAtMost32, 

Important traits for &'_ [u8]

impl<'_> Read for &'_ [u8]impl<'_> Write for &'_ mut [u8]

fn as_mut(&mut self) -> &mut [T]

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