Struct core::cell::RefMut

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

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

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.

Example

fn main() { 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')); }

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'));

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

Deprecated since 1.8.0

: can be built on RefMut::map: https://crates.io/crates/ref_filter_map

Unstable (cell_extras #27746)

: can be built on RefMut::map: https://crates.io/crates/ref_filter_map

Make a new RefMut for an optional 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::filter_map(...). A method would interfere with methods of the same name on the contents of a RefCell used through Deref.

Example

#![feature(cell_extras)] fn main() { use std::cell::{RefCell, RefMut}; let c = RefCell::new(Ok(5)); { let b1: RefMut<Result<u32, ()>> = c.borrow_mut(); let mut b2: RefMut<u32> = RefMut::filter_map(b1, |o| { o.as_mut().ok() }).unwrap(); assert_eq!(*b2, 5); *b2 = 42; } assert_eq!(*c.borrow(), Ok(42)); }

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

let c = RefCell::new(Ok(5));
{
    let b1: RefMut<Result<u32, ()>> = c.borrow_mut();
    let mut b2: RefMut<u32> = RefMut::filter_map(b1, |o| {
        o.as_mut().ok()
    }).unwrap();
    assert_eq!(*b2, 5);
    *b2 = 42;
}
assert_eq!(*c.borrow(), Ok(42));

Trait Implementations

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

type Target = T

The resulting type after dereferencing

fn deref(&self) -> &T

The method called to dereference a value

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

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

The method called to mutably dereference a value

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

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

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

Formats the value using the given formatter.