Struct std::cell::RefMut

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

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

Make 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'));

Trait Implementations

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

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

Formats the value using the given formatter.

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

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

Important traits for &'a mut I

impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W

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

Mutably dereferences the value.

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

type Target = T

The resulting type after dereferencing.

Important traits for &'a mut I

impl<'a, I> Iterator for &'a mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W

fn deref(&self) -> &T

Dereferences the value.

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

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

Formats the value using the given formatter.