std::convert::AsMut - Rust
Description: API documentation for the Rust `AsMut` trait in crate `std`.
Keywords: rust, rustlang, rust-lang, AsMut

# 1.0.0[−][src]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);

Run

## Required methods

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

Performs the conversion.

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## Implementors

### `impl AsMut<str> for String`[src]

#### `fn as_mut(&mut self) -> &mut str`[src]

### `impl<'_, T, U> AsMut<U> for &'_ mut T where
T: AsMut<U> + ?Sized,
U: ?Sized,` [src]

#### `fn as_mut(&mut self) -> &mut U`[src]

### `impl<T> AsMut<[T]> for [T]`[src]

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

### `impl<T> AsMut<[T]> for Vec<T>`[src]

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

### `impl<T> AsMut<Vec<T>> for Vec<T>`[src]

#### `fn as_mut(&mut self) -> &mut Vec<T>`[src]

### `impl<T> AsMut<T> for Box<T> where
T: ?Sized,` [src]

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

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

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

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