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

# 1.0.0[−][src]Struct core::cell::RefMut

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

A wrapper type for a mutably borrowed value from a `RefCell<T>`.

See the module-level documentation for more.

## Methods

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

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

Makes a new `RefMut` for a component of the borrowed data, e.g., an enum variant.

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

This is an associated function that needs to be used as `RefMut::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, RefMut};

    let c = RefCell::new((5, 'b'));
    {
        let b1: RefMut<(u32, char)> = c.borrow_mut();
        let mut b2: RefMut<u32> = RefMut::map(b1, |t| &mut t.0);
        assert_eq!(*b2, 5);
        *b2 = 42;
    }
    assert_eq!(*c.borrow(), (42, 'b'));Run

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

Splits a `RefMut` into multiple `RefMut`s for different components of the borrowed data.

The underlying `RefCell` will remain mutably borrowed until both returned `RefMut`s go out of scope.

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

This is an associated function that needs to be used as `RefMut::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::{RefCell, RefMut};

    let cell = RefCell::new([1, 2, 3, 4]);
    let borrow = cell.borrow_mut();
    let (mut begin, mut end) = RefMut::map_split(borrow, |slice| slice.split_at_mut(2));
    assert_eq!(*begin, [1, 2]);
    assert_eq!(*end, [3, 4]);
    begin.copy_from_slice(&[4, 3]);
    end.copy_from_slice(&[2, 1]);Run

## Trait Implementations

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

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

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

Formats the value using the given formatter. Read more

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

#### `type Target = T`

The resulting type after dereferencing.

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

Dereferences the value.

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

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

Mutably dereferences the value.

### `impl<'_, T: ?Sized + Display> Display for RefMut<'_, 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 RefMut<'b, T>`

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

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