# 1.0.0[−][src]Struct core::cell::Ref

    pub struct Ref<'b, T: ?Sized + 'b> { /* 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.

## Implementations

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

#### `pub 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`.

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

Makes 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

#### `pub fn map_split<U: ?Sized, V: ?Sized, F>(
orig: Ref<'b, T>,
f: F
) -> (Ref<'b, U>, Ref<'b, V>) where
F: FnOnce(&T) -> (&U, &V),` 1.35.0[src]

Splits a `Ref` into multiple `Ref`s for different components 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_split(...)`. A method would interfere with methods of the same name on the contents of a `RefCell` used through `Deref`.

# Examples

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

    let cell = RefCell::new([1, 2, 3, 4]);
    let borrow = cell.borrow();
    let (begin, end) = Ref::map_split(borrow, |slice| slice.split_at(2));
    assert_eq!(*begin, [1, 2]);
    assert_eq!(*end, [3, 4]);

Run

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

🔬 This is a nightly-only experimental API. (`cell_leak` #69099)

Convert into a reference to the underlying data.

The underlying `RefCell` can never be mutably borrowed from again and will always appear already immutably borrowed. It is not a good idea to leak more than a constant number of references. The `RefCell` can be immutably borrowed again if only a smaller number of leaks have occurred in total.

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

# Examples

    #![feature(cell_leak)]
    use std::cell::{RefCell, Ref};
    let cell = RefCell::new(0);

    let value = Ref::leak(cell.borrow());
    assert_eq!(*value, 0);

    assert!(cell.try_borrow().is_ok());
    assert!(cell.try_borrow_mut().is_err());

Run

## Trait Implementations

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

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

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

Formats the value using the given formatter. Read more

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

#### `type Target = T`

The resulting type after dereferencing.

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

Dereferences the value.

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

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

Formats the value using the given formatter. Read more

## Auto Trait Implementations

### `impl<'b, T> !Send for Ref<'b, T>`

### `impl<'b, T> !Sync for Ref<'b, T>`

### `impl<'b, T: ?Sized> Unpin for Ref<'b, T>`

## Blanket Implementations

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `fn type_id(&Self) -> TypeId`[src]

Gets the `TypeId` of `self`. Read more

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

#### `fn borrow(&Self) -> &T`[src]

Immutably borrows from an owned value. Read more

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

#### `fn borrow_mut(&mut Self) -> &mut T`[src]

Mutably borrows from an owned value. Read more

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

#### `fn from(T) -> T`[src]

Performs the conversion.

### `impl<T, U> Into<U> for T where
U: From<T>,` [src]

#### `fn into(Self) -> U`[src]

Performs the conversion.

### `impl<T, U> TryFrom<U> for T where
U: Into<T>,` [src]

#### `type Error = Infallible`

The type returned in the event of a conversion error.

#### `fn try_from(U) -> Result<T, <T as TryFrom<U>>::Error>`[src]

Performs the conversion.

### `impl<T, U> TryInto<U> for T where
U: TryFrom<T>,` [src]

#### `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>`[src]

Performs the conversion.