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>

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

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'));

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), 

🔬 This is a nightly-only experimental API. (refcell_map_split #51476)

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

The underlying RefCell will remain mutably borrowed until both returned RefMuts 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

#![feature(refcell_map_split)]
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]);

Trait Implementations

impl<T: ?Sized, '_> Deref for RefMut<'_, T>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &T

Dereferences the value.

impl<T: ?Sized, '_> DerefMut for RefMut<'_, T>

fn deref_mut(&mut self) -> &mut T

Mutably dereferences the value.

impl<'b, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<RefMut<'b, U>> for RefMut<'b, T>

impl<T: ?Sized + Debug, '_> Debug for RefMut<'_, T>

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

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

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.