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

# 1.0.0[−][src]Trait core::convert::AsRef

    pub trait AsRef<T: ?Sized> {
        fn as_ref(&self) -> &T;
    }

A cheap reference-to-reference conversion. Used to convert a value to a reference value within generic code.

`AsRef` is very similar to, but serves a slightly different purpose than, `Borrow`.

`AsRef` is to be used when wishing to convert to a reference of another type. `Borrow` is more related to the notion of taking the reference. It is useful when wishing to abstract over the type of reference (`&T`, `&mut T`) or allow both the referenced and owned type to be treated in the same manner.

The key difference between the two traits is the intention:

- Use `AsRef` when the goal is to simply convert into a reference
- Use `Borrow` when the goal is related to writing code that is agnostic to the type of borrow and whether it is a reference or value

See the book for a more detailed comparison.

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

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

# Examples

Both `String` and `&str` implement `AsRef<str>`:

    fn is_hello<T: AsRef<str>>(s: T) {
       assert_eq!("hello", s.as_ref());
    }

    let s = "hello";
    is_hello(s);

    let s = "hello".to_string();
    is_hello(s);Run

## Required methods

### `fn as_ref(&self) -> &T`

Performs the conversion.

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## Implementors

### `impl AsRef<[u8]> for str`[src]

#### `fn as_ref(&self) -> &[u8]`[src]

### `impl AsRef<str> for str`[src]

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

### `impl<T> AsRef<[T]> for [T; 0]`[src]

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

### `impl<T> AsRef<[T]> for [T; 1]`[src]

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

### `impl<T> AsRef<[T]> for [T; 2]`[src]

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

### `impl<T> AsRef<[T]> for [T; 3]`[src]

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

### `impl<T> AsRef<[T]> for [T; 4]`[src]

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

### `impl<T> AsRef<[T]> for [T; 5]`[src]

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

### `impl<T> AsRef<[T]> for [T; 6]`[src]

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

### `impl<T> AsRef<[T]> for [T; 7]`[src]

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

### `impl<T> AsRef<[T]> for [T; 8]`[src]

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

### `impl<T> AsRef<[T]> for [T; 9]`[src]

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

### `impl<T> AsRef<[T]> for [T; 10]`[src]

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

### `impl<T> AsRef<[T]> for [T; 11]`[src]

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

### `impl<T> AsRef<[T]> for [T; 12]`[src]

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

### `impl<T> AsRef<[T]> for [T; 13]`[src]

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

### `impl<T> AsRef<[T]> for [T; 14]`[src]

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

### `impl<T> AsRef<[T]> for [T; 15]`[src]

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

### `impl<T> AsRef<[T]> for [T; 16]`[src]

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

### `impl<T> AsRef<[T]> for [T; 17]`[src]

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

### `impl<T> AsRef<[T]> for [T; 18]`[src]

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

### `impl<T> AsRef<[T]> for [T; 19]`[src]

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

### `impl<T> AsRef<[T]> for [T; 20]`[src]

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

### `impl<T> AsRef<[T]> for [T; 21]`[src]

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

### `impl<T> AsRef<[T]> for [T; 22]`[src]

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

### `impl<T> AsRef<[T]> for [T; 23]`[src]

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

### `impl<T> AsRef<[T]> for [T; 24]`[src]

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

### `impl<T> AsRef<[T]> for [T; 25]`[src]

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

### `impl<T> AsRef<[T]> for [T; 26]`[src]

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

### `impl<T> AsRef<[T]> for [T; 27]`[src]

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

### `impl<T> AsRef<[T]> for [T; 28]`[src]

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

### `impl<T> AsRef<[T]> for [T; 29]`[src]

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

### `impl<T> AsRef<[T]> for [T; 30]`[src]

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

### `impl<T> AsRef<[T]> for [T; 31]`[src]

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

### `impl<T> AsRef<[T]> for [T; 32]`[src]

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

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

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

### `impl<T, '_> AsRef<[T]> for Iter<'_, T>`[src]

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

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

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

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

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

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