pub struct RefCell<T> where
T: ?Sized, { /* private fields */ }
Expand description
A mutable memory location with dynamically checked borrow rules
See the module-level documentation for more.
Implementations
sourceimpl<T> RefCell<T>
impl<T> RefCell<T>
const: unstable · sourcepub fn into_inner(self) -> T
pub fn into_inner(self) -> T
1.24.0 · sourcepub fn replace(&self, t: T) -> T
pub fn replace(&self, t: T) -> T
Replaces the wrapped value with a new one, returning the old value, without deinitializing either one.
This function corresponds to std::mem::replace
.
Panics
Panics if the value is currently borrowed.
Examples
use std::cell::RefCell;
let cell = RefCell::new(5);
let old_value = cell.replace(6);
assert_eq!(old_value, 5);
assert_eq!(cell, RefCell::new(6));
Run1.35.0 · sourcepub fn replace_with<F>(&self, f: F) -> T where
F: FnOnce(&mut T) -> T,
pub fn replace_with<F>(&self, f: F) -> T where
F: FnOnce(&mut T) -> T,
Replaces the wrapped value with a new one computed from f
, returning
the old value, without deinitializing either one.
Panics
Panics if the value is currently borrowed.
Examples
use std::cell::RefCell;
let cell = RefCell::new(5);
let old_value = cell.replace_with(|&mut old| old + 1);
assert_eq!(old_value, 5);
assert_eq!(cell, RefCell::new(6));
Run1.24.0 · sourcepub fn swap(&self, other: &RefCell<T>)
pub fn swap(&self, other: &RefCell<T>)
Swaps the wrapped value of self
with the wrapped value of other
,
without deinitializing either one.
This function corresponds to std::mem::swap
.
Panics
Panics if the value in either RefCell
is currently borrowed.
Examples
use std::cell::RefCell;
let c = RefCell::new(5);
let d = RefCell::new(6);
c.swap(&d);
assert_eq!(c, RefCell::new(6));
assert_eq!(d, RefCell::new(5));
Runsourceimpl<T> RefCell<T> where
T: ?Sized,
impl<T> RefCell<T> where
T: ?Sized,
sourcepub fn borrow(&self) -> Ref<'_, T>
pub fn borrow(&self) -> Ref<'_, T>
Immutably borrows the wrapped value.
The borrow lasts until the returned Ref
exits scope. Multiple
immutable borrows can be taken out at the same time.
Panics
Panics if the value is currently mutably borrowed. For a non-panicking variant, use
try_borrow
.
Examples
use std::cell::RefCell;
let c = RefCell::new(5);
let borrowed_five = c.borrow();
let borrowed_five2 = c.borrow();
RunAn example of panic:
use std::cell::RefCell;
let c = RefCell::new(5);
let m = c.borrow_mut();
let b = c.borrow(); // this causes a panic
Run1.13.0 · sourcepub fn try_borrow(&self) -> Result<Ref<'_, T>, BorrowError>
pub fn try_borrow(&self) -> Result<Ref<'_, T>, BorrowError>
Immutably borrows the wrapped value, returning an error if the value is currently mutably borrowed.
The borrow lasts until the returned Ref
exits scope. Multiple immutable borrows can be
taken out at the same time.
This is the non-panicking variant of borrow
.
Examples
use std::cell::RefCell;
let c = RefCell::new(5);
{
let m = c.borrow_mut();
assert!(c.try_borrow().is_err());
}
{
let m = c.borrow();
assert!(c.try_borrow().is_ok());
}
Runsourcepub fn borrow_mut(&self) -> RefMut<'_, T>
pub fn borrow_mut(&self) -> RefMut<'_, T>
Mutably borrows the wrapped value.
The borrow lasts until the returned RefMut
or all RefMut
s derived
from it exit scope. The value cannot be borrowed while this borrow is
active.
Panics
Panics if the value is currently borrowed. For a non-panicking variant, use
try_borrow_mut
.
Examples
use std::cell::RefCell;
let c = RefCell::new("hello".to_owned());
*c.borrow_mut() = "bonjour".to_owned();
assert_eq!(&*c.borrow(), "bonjour");
RunAn example of panic:
use std::cell::RefCell;
let c = RefCell::new(5);
let m = c.borrow();
let b = c.borrow_mut(); // this causes a panic
Run1.13.0 · sourcepub fn try_borrow_mut(&self) -> Result<RefMut<'_, T>, BorrowMutError>
pub fn try_borrow_mut(&self) -> Result<RefMut<'_, T>, BorrowMutError>
Mutably borrows the wrapped value, returning an error if the value is currently borrowed.
The borrow lasts until the returned RefMut
or all RefMut
s derived
from it exit scope. The value cannot be borrowed while this borrow is
active.
This is the non-panicking variant of borrow_mut
.
Examples
use std::cell::RefCell;
let c = RefCell::new(5);
{
let m = c.borrow();
assert!(c.try_borrow_mut().is_err());
}
assert!(c.try_borrow_mut().is_ok());
Run1.11.0 · sourcepub fn get_mut(&mut self) -> &mut T
pub fn get_mut(&mut self) -> &mut T
Returns a mutable reference to the underlying data.
This call borrows RefCell
mutably (at compile-time) so there is no
need for dynamic checks.
However be cautious: this method expects self
to be mutable, which is
generally not the case when using a RefCell
. Take a look at the
borrow_mut
method instead if self
isn’t mutable.
Also, please be aware that this method is only for special circumstances and is usually
not what you want. In case of doubt, use borrow_mut
instead.
Examples
use std::cell::RefCell;
let mut c = RefCell::new(5);
*c.get_mut() += 1;
assert_eq!(c, RefCell::new(6));
Runsourcepub fn undo_leak(&mut self) -> &mut T
pub fn undo_leak(&mut self) -> &mut T
Undo the effect of leaked guards on the borrow state of the RefCell
.
This call is similar to get_mut
but more specialized. It borrows RefCell
mutably to
ensure no borrows exist and then resets the state tracking shared borrows. This is relevant
if some Ref
or RefMut
borrows have been leaked.
Examples
#![feature(cell_leak)]
use std::cell::RefCell;
let mut c = RefCell::new(0);
std::mem::forget(c.borrow_mut());
assert!(c.try_borrow().is_err());
c.undo_leak();
assert!(c.try_borrow().is_ok());
Run1.37.0 · sourcepub unsafe fn try_borrow_unguarded(&self) -> Result<&T, BorrowError>
pub unsafe fn try_borrow_unguarded(&self) -> Result<&T, BorrowError>
Immutably borrows the wrapped value, returning an error if the value is currently mutably borrowed.
Safety
Unlike RefCell::borrow
, this method is unsafe because it does not
return a Ref
, thus leaving the borrow flag untouched. Mutably
borrowing the RefCell
while the reference returned by this method
is alive is undefined behaviour.
Examples
use std::cell::RefCell;
let c = RefCell::new(5);
{
let m = c.borrow_mut();
assert!(unsafe { c.try_borrow_unguarded() }.is_err());
}
{
let m = c.borrow();
assert!(unsafe { c.try_borrow_unguarded() }.is_ok());
}
RunTrait Implementations
1.10.0 · sourceimpl<T> Ord for RefCell<T> where
T: Ord + ?Sized,
impl<T> Ord for RefCell<T> where
T: Ord + ?Sized,
sourcefn cmp(&self, other: &RefCell<T>) -> Ordering
fn cmp(&self, other: &RefCell<T>) -> Ordering
Panics
Panics if the value in either RefCell
is currently borrowed.
1.21.0 · sourcefn max(self, other: Self) -> Self
fn max(self, other: Self) -> Self
Compares and returns the maximum of two values. Read more
1.10.0 · sourceimpl<T> PartialOrd<RefCell<T>> for RefCell<T> where
T: PartialOrd<T> + ?Sized,
impl<T> PartialOrd<RefCell<T>> for RefCell<T> where
T: PartialOrd<T> + ?Sized,
sourcefn partial_cmp(&self, other: &RefCell<T>) -> Option<Ordering>
fn partial_cmp(&self, other: &RefCell<T>) -> Option<Ordering>
Panics
Panics if the value in either RefCell
is currently borrowed.
sourcefn lt(&self, other: &RefCell<T>) -> bool
fn lt(&self, other: &RefCell<T>) -> bool
Panics
Panics if the value in either RefCell
is currently borrowed.
sourcefn le(&self, other: &RefCell<T>) -> bool
fn le(&self, other: &RefCell<T>) -> bool
Panics
Panics if the value in either RefCell
is currently borrowed.
impl<T, U> CoerceUnsized<RefCell<U>> for RefCell<T> where
T: CoerceUnsized<U>,
impl<T> Eq for RefCell<T> where
T: Eq + ?Sized,
impl<T> Send for RefCell<T> where
T: Send + ?Sized,
impl<T> !Sync for RefCell<T> where
T: ?Sized,
Auto Trait Implementations
impl<T> !RefUnwindSafe for RefCell<T>
impl<T: ?Sized> Unpin for RefCell<T> where
T: Unpin,
impl<T: ?Sized> UnwindSafe for RefCell<T> where
T: UnwindSafe,
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more