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.
Implementations
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 filter_map<U, F>(
orig: RefMut<'b, T>,
f: F
) -> Result<RefMut<'b, U>, RefMut<'b, T>> where
F: FnOnce(&mut T) -> Option<&mut U>,
U: ?Sized,
cell_filter_map
#81061)recently added
Makes a new RefMut
for an optional component of the borrowed data. The original guard is returned as an Err(..)
if the closure returns None
.
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
.
Examples
#![feature(cell_filter_map)] use std::cell::{RefCell, RefMut}; let c = RefCell::new(vec![1, 2, 3]); { let b1: RefMut<Vec<u32>> = c.borrow_mut(); let mut b2: Result<RefMut<u32>, _> = RefMut::filter_map(b1, |v| v.get_mut(1)); if let Ok(mut b2) = b2 { *b2 += 2; } } assert_eq!(*c.borrow(), vec![1, 4, 3]);
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]);
pub fn leak(orig: RefMut<'b, T>) -> &'b mut T
Convert into a mutable reference to the underlying data.
The underlying RefCell
can not be borrowed from again and will always appear already mutably borrowed, making the returned reference the only to the interior.
This is an associated function that needs to be used as RefMut::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, RefMut}; let cell = RefCell::new(0); let value = RefMut::leak(cell.borrow_mut()); assert_eq!(*value, 0); *value = 1; assert!(cell.try_borrow_mut().is_err());
Trait Implementations
pub fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>
Formats the value using the given formatter. Read more
type Target = T
The resulting type after dereferencing.
pub fn deref(&self) -> &T
Dereferences the value.
pub fn deref_mut(&mut self) -> &mut T
Mutably dereferences the value.
pub fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>
Formats the value using the given formatter. Read more
Auto Trait Implementations
impl<'b, T> !RefUnwindSafe for RefMut<'b, T>
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>
impl<'b, T> !UnwindSafe for RefMut<'b, T>
Blanket Implementations
impl<T> From<T> for T
pub fn from(t: T) -> T
Performs the conversion.
pub fn into(self) -> U
Performs the conversion.
type Error = Infallible
The type returned in the event of a conversion error.
pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
Performs the conversion.
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
Performs the conversion.
© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/cell/struct.RefMut.html