std::cell::Ref - Rust
Description: API documentation for the Rust `Ref` struct in crate `std`.
Keywords: rust, rustlang, rust-lang, Ref

# Struct std::cell::Ref 1.0.0 [−] [src]

    pub struct Ref<'b, T> where
        T: 'b + ?Sized,  { /* fields omitted */ }

Wraps a borrowed reference to a value in a `RefCell` box. A wrapper type for an immutably borrowed value from a `RefCell<T>`.

See the module-level documentation for more.

## Methods

### `impl<'b, T> Ref<'b, T> where
T: ?Sized,`
[src]

#### `fn clone(orig: &Ref<'b, T>) -> Ref<'b, T>`
1.15.0
[src]

Copies a `Ref`.

The `RefCell` is already immutably borrowed, so this cannot fail.

This is an associated function that needs to be used as `Ref::clone(...)`. A `Clone` implementation or a method would interfere with the widespread use of `r.borrow().clone()` to clone the contents of a `RefCell`.

#### `fn map<U, F>(orig: Ref<'b, T>, f: F) -> Ref<'b, U> where
F: FnOnce(&T) -> &U,
U: ?Sized,`
1.8.0
[src]

Make a new `Ref` for a component of the borrowed data.

The `RefCell` is already immutably borrowed, so this cannot fail.

This is an associated function that needs to be used as `Ref::map(...)`. A method would interfere with methods of the same name on the contents of a `RefCell` used through `Deref`.

# Examples

    use std::cell::{RefCell, Ref};

    let c = RefCell::new((5, 'b'));
    let b1: Ref<(u32, char)> = c.borrow();
    let b2: Ref<u32> = Ref::map(b1, |t| &t.0);
    assert_eq!(*b2, 5)Run

## Trait Implementations

### `impl<'b, T, U> CoerceUnsized<Ref<'b, U>> for Ref<'b, T> where
T: Unsize<U> + ?Sized,
U: ?Sized,`
[src]

### `impl<'a, T> Display for Ref<'a, T> where
T: Display + ?Sized,`
1.20.0
[src]

#### `fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`
[src]

Formats the value using the given formatter. Read more

### `impl<'b, T> Deref for Ref<'b, T> where
T: ?Sized,`
[src]

#### `type Target = T`

The resulting type after dereferencing.

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

Dereferences the value.

### `impl<'b, T> Debug for Ref<'b, T> where
T: Debug + ?Sized,`
[src]

#### `fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`
[src]

Formats the value using the given formatter.

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