#[repr(transparent)]pub struct Cell<T> where
T: ?Sized, { /* private fields */ }
Expand description
A mutable memory location.
Examples
In this example, you can see that Cell<T>
enables mutation inside an
immutable struct. In other words, it enables “interior mutability”.
use std::cell::Cell;
struct SomeStruct {
regular_field: u8,
special_field: Cell<u8>,
}
let my_struct = SomeStruct {
regular_field: 0,
special_field: Cell::new(1),
};
let new_value = 100;
// ERROR: `my_struct` is immutable
// my_struct.regular_field = new_value;
// WORKS: although `my_struct` is immutable, `special_field` is a `Cell`,
// which can always be mutated
my_struct.special_field.set(new_value);
assert_eq!(my_struct.special_field.get(), new_value);
See the module-level documentation for more.
Implementations
sourceimpl<T> Cell<T>
impl<T> Cell<T>
1.17.0 · sourcepub fn swap(&self, other: &Cell<T>)
pub fn swap(&self, other: &Cell<T>)
Swaps the values of two Cell
s.
Difference with std::mem::swap
is that this function doesn’t require &mut
reference.
Examples
use std::cell::Cell;
let c1 = Cell::new(5i32);
let c2 = Cell::new(10i32);
c1.swap(&c2);
assert_eq!(10, c1.get());
assert_eq!(5, c2.get());
1.17.0 · sourcepub fn replace(&self, val: T) -> T
pub fn replace(&self, val: T) -> T
Replaces the contained value with val
, and returns the old contained value.
Examples
use std::cell::Cell;
let cell = Cell::new(5);
assert_eq!(cell.get(), 5);
assert_eq!(cell.replace(10), 5);
assert_eq!(cell.get(), 10);
1.17.0 (const: unstable) · sourcepub fn into_inner(self) -> T
pub fn into_inner(self) -> T
Unwraps the value.
Examples
use std::cell::Cell;
let c = Cell::new(5);
let five = c.into_inner();
assert_eq!(five, 5);
sourceimpl<T> Cell<T> where
T: Copy,
impl<T> Cell<T> where
T: Copy,
sourcepub fn get(&self) -> T
pub fn get(&self) -> T
Returns a copy of the contained value.
Examples
use std::cell::Cell;
let c = Cell::new(5);
let five = c.get();
sourcepub fn update<F>(&self, f: F) -> T where
F: FnOnce(T) -> T,
🔬 This is a nightly-only experimental API. (cell_update
)
pub fn update<F>(&self, f: F) -> T where
F: FnOnce(T) -> T,
cell_update
)Updates the contained value using a function and returns the new value.
Examples
#![feature(cell_update)]
use std::cell::Cell;
let c = Cell::new(5);
let new = c.update(|x| x + 1);
assert_eq!(new, 6);
assert_eq!(c.get(), 6);
sourceimpl<T> Cell<T> where
T: ?Sized,
impl<T> Cell<T> where
T: ?Sized,
1.12.0 (const: 1.32.0) · sourcepub const fn as_ptr(&self) -> *mut T
pub const fn as_ptr(&self) -> *mut T
Returns a raw pointer to the underlying data in this cell.
Examples
use std::cell::Cell;
let c = Cell::new(5);
let ptr = c.as_ptr();
1.11.0 · 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 Cell
mutably (at compile-time) which guarantees
that we possess the only reference.
However be cautious: this method expects self
to be mutable, which is
generally not the case when using a Cell
. If you require interior
mutability by reference, consider using RefCell
which provides
run-time checked mutable borrows through its borrow_mut
method.
Examples
use std::cell::Cell;
let mut c = Cell::new(5);
*c.get_mut() += 1;
assert_eq!(c.get(), 6);
1.37.0 · sourcepub fn from_mut(t: &mut T) -> &Cell<T>
pub fn from_mut(t: &mut T) -> &Cell<T>
Returns a &Cell<T>
from a &mut T
Examples
use std::cell::Cell;
let slice: &mut [i32] = &mut [1, 2, 3];
let cell_slice: &Cell<[i32]> = Cell::from_mut(slice);
let slice_cell: &[Cell<i32>] = cell_slice.as_slice_of_cells();
assert_eq!(slice_cell.len(), 3);
sourceimpl<T> Cell<[T]>
impl<T> Cell<[T]>
1.37.0 · sourcepub fn as_slice_of_cells(&self) -> &[Cell<T>]
pub fn as_slice_of_cells(&self) -> &[Cell<T>]
Returns a &[Cell<T>]
from a &Cell<[T]>
Examples
use std::cell::Cell;
let slice: &mut [i32] = &mut [1, 2, 3];
let cell_slice: &Cell<[i32]> = Cell::from_mut(slice);
let slice_cell: &[Cell<i32>] = cell_slice.as_slice_of_cells();
assert_eq!(slice_cell.len(), 3);
sourceimpl<T, const N: usize> Cell<[T; N]>
impl<T, const N: usize> Cell<[T; N]>
sourcepub fn as_array_of_cells(&self) -> &[Cell<T>; N]
🔬 This is a nightly-only experimental API. (as_array_of_cells
)
pub fn as_array_of_cells(&self) -> &[Cell<T>; N]
as_array_of_cells
)Returns a &[Cell<T>; N]
from a &Cell<[T; N]>
Examples
#![feature(as_array_of_cells)]
use std::cell::Cell;
let mut array: [i32; 3] = [1, 2, 3];
let cell_array: &Cell<[i32; 3]> = Cell::from_mut(&mut array);
let array_cell: &[Cell<i32>; 3] = cell_array.as_array_of_cells();
Trait Implementations
sourceimpl<T> ConstDefault for Cell<T> where
T: ConstDefault,
impl<T> ConstDefault for Cell<T> where
T: ConstDefault,
sourceimpl<'de, T> Deserialize<'de> for Cell<T> where
T: Deserialize<'de> + Copy,
impl<'de, T> Deserialize<'de> for Cell<T> where
T: Deserialize<'de> + Copy,
sourcefn deserialize<D>(
deserializer: D
) -> Result<Cell<T>, <D as Deserializer<'de>>::Error> where
D: Deserializer<'de>,
fn deserialize<D>(
deserializer: D
) -> Result<Cell<T>, <D as Deserializer<'de>>::Error> where
D: Deserializer<'de>,
Deserialize this value from the given Serde deserializer. Read more
sourceimpl<'de, T, U> DeserializeAs<'de, Cell<T>> for Cell<U> where
U: DeserializeAs<'de, T>,
impl<'de, T, U> DeserializeAs<'de, Cell<T>> for Cell<U> where
U: DeserializeAs<'de, T>,
sourcefn deserialize_as<D>(
deserializer: D
) -> Result<Cell<T>, <D as Deserializer<'de>>::Error> where
D: Deserializer<'de>,
fn deserialize_as<D>(
deserializer: D
) -> Result<Cell<T>, <D as Deserializer<'de>>::Error> where
D: Deserializer<'de>,
Deserialize this value from the given Serde deserializer.
1.10.0 · sourceimpl<T> Ord for Cell<T> where
T: Ord + Copy,
impl<T> Ord for Cell<T> where
T: Ord + Copy,
1.10.0 · sourceimpl<T> PartialOrd<Cell<T>> for Cell<T> where
T: PartialOrd<T> + Copy,
impl<T> PartialOrd<Cell<T>> for Cell<T> where
T: PartialOrd<T> + Copy,
sourcefn partial_cmp(&self, other: &Cell<T>) -> Option<Ordering>
fn partial_cmp(&self, other: &Cell<T>) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Cell<T>) -> bool
fn lt(&self, other: &Cell<T>) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Cell<T>) -> bool
fn le(&self, other: &Cell<T>) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
sourceimpl<T> Serialize for Cell<T> where
T: Serialize + Copy,
impl<T> Serialize for Cell<T> where
T: Serialize + Copy,
sourcefn serialize<S>(
&self,
serializer: S
) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error> where
S: Serializer,
fn serialize<S>(
&self,
serializer: S
) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error> where
S: Serializer,
Serialize this value into the given Serde serializer. Read more
sourceimpl<T, U> SerializeAs<Cell<T>> for Cell<U> where
U: SerializeAs<T>,
T: Copy,
impl<T, U> SerializeAs<Cell<T>> for Cell<U> where
U: SerializeAs<T>,
T: Copy,
sourcefn serialize_as<S>(
source: &Cell<T>,
serializer: S
) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error> where
S: Serializer,
fn serialize_as<S>(
source: &Cell<T>,
serializer: S
) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error> where
S: Serializer,
Serialize this value into the given Serde serializer.
impl<T, U> CoerceUnsized<Cell<U>> for Cell<T> where
T: CoerceUnsized<U>,
impl<T> Eq for Cell<T> where
T: Eq + Copy,
impl<T> Send for Cell<T> where
T: Send + ?Sized,
impl<T> !Sync for Cell<T> where
T: ?Sized,
Auto Trait Implementations
impl<T> !RefUnwindSafe for Cell<T>
impl<T: ?Sized> Unpin for Cell<T> where
T: Unpin,
impl<T: ?Sized> UnwindSafe for Cell<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
impl<T> Downcast for T where
T: Any,
impl<T> Downcast for T where
T: Any,
fn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>ⓘNotable traits for Box<W, Global>impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;
fn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>ⓘNotable traits for Box<W, Global>impl<W> Write for Box<W, Global> where
W: Write + ?Sized, impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;
W: Write + ?Sized, impl<R> Read for Box<R, Global> where
R: Read + ?Sized, impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;
Convert Box<dyn Trait>
(where Trait: Downcast
) to Box<dyn Any>
. Box<dyn Any>
can
then be further downcast
into Box<ConcreteType>
where ConcreteType
implements Trait
. Read more
fn into_any_rc(self: Rc<T>) -> Rc<dyn Any + 'static>
fn into_any_rc(self: Rc<T>) -> Rc<dyn Any + 'static>
Convert Rc<Trait>
(where Trait: Downcast
) to Rc<Any>
. Rc<Any>
can then be
further downcast
into Rc<ConcreteType>
where ConcreteType
implements Trait
. Read more
fn as_any(&self) -> &(dyn Any + 'static)
fn as_any(&self) -> &(dyn Any + 'static)
Convert &Trait
(where Trait: Downcast
) to &Any
. This is needed since Rust cannot
generate &Any
’s vtable from &Trait
’s. Read more
fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
Convert &mut Trait
(where Trait: Downcast
) to &Any
. This is needed since Rust cannot
generate &mut Any
’s vtable from &mut Trait
’s. Read more
impl<A> DynCastExt for A
impl<A> DynCastExt for A
fn dyn_cast<T>(
self
) -> Result<<A as DynCastExtHelper<T>>::Target, <A as DynCastExtHelper<T>>::Source> where
A: DynCastExtHelper<T>,
T: ?Sized,
fn dyn_cast<T>(
self
) -> Result<<A as DynCastExtHelper<T>>::Target, <A as DynCastExtHelper<T>>::Source> where
A: DynCastExtHelper<T>,
T: ?Sized,
Use this to cast from one trait object type to another. Read more
fn dyn_upcast<T>(self) -> <A as DynCastExtAdvHelper<T, T>>::Target where
A: DynCastExtAdvHelper<T, T, Source = <A as DynCastExtAdvHelper<T, T>>::Target>,
T: ?Sized,
fn dyn_upcast<T>(self) -> <A as DynCastExtAdvHelper<T, T>>::Target where
A: DynCastExtAdvHelper<T, T, Source = <A as DynCastExtAdvHelper<T, T>>::Target>,
T: ?Sized,
Use this to upcast a trait to one of its supertraits. Read more
fn dyn_cast_adv<F, T>(
self
) -> Result<<A as DynCastExtAdvHelper<F, T>>::Target, <A as DynCastExtAdvHelper<F, T>>::Source> where
A: DynCastExtAdvHelper<F, T>,
F: ?Sized,
T: ?Sized,
fn dyn_cast_adv<F, T>(
self
) -> Result<<A as DynCastExtAdvHelper<F, T>>::Target, <A as DynCastExtAdvHelper<F, T>>::Source> where
A: DynCastExtAdvHelper<F, T>,
F: ?Sized,
T: ?Sized,
fn dyn_cast_with_config<C>(
self
) -> Result<<A as DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>>::Target, <A as DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>>::Source> where
C: DynCastConfig,
A: DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>,
fn dyn_cast_with_config<C>(
self
) -> Result<<A as DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>>::Target, <A as DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>>::Source> where
C: DynCastConfig,
A: DynCastExtAdvHelper<<C as DynCastConfig>::Source, <C as DynCastConfig>::Target>,
Use this to cast from one trait object type to another. With this method the type parameter is a config type that uniquely specifies which cast should be preformed. Read more
sourceimpl<Q, K> Equivalent<K> for Q where
Q: Eq + ?Sized,
K: Borrow<Q> + ?Sized,
impl<Q, K> Equivalent<K> for Q where
Q: Eq + ?Sized,
K: Borrow<Q> + ?Sized,
sourcefn equivalent(&self, key: &K) -> bool
fn equivalent(&self, key: &K) -> bool
Compare self to key
and return true
if they are equal.
sourceimpl<T> Instrument for T
impl<T> Instrument for T
sourcefn instrument(self, span: Span) -> Instrumented<Self>ⓘNotable traits for Instrumented<T>impl<T> Future for Instrumented<T> where
T: Future, type Output = <T as Future>::Output;
fn instrument(self, span: Span) -> Instrumented<Self>ⓘNotable traits for Instrumented<T>impl<T> Future for Instrumented<T> where
T: Future, type Output = <T as Future>::Output;
T: Future, type Output = <T as Future>::Output;
sourcefn in_current_span(self) -> Instrumented<Self>ⓘNotable traits for Instrumented<T>impl<T> Future for Instrumented<T> where
T: Future, type Output = <T as Future>::Output;
fn in_current_span(self) -> Instrumented<Self>ⓘNotable traits for Instrumented<T>impl<T> Future for Instrumented<T> where
T: Future, type Output = <T as Future>::Output;
T: Future, type Output = <T as Future>::Output;
sourceimpl<T> Serialize for T where
T: Serialize + ?Sized,
impl<T> Serialize for T where
T: Serialize + ?Sized,
fn erased_serialize(&self, serializer: &mut dyn Serializer) -> Result<Ok, Error>
impl<V, T> VZip<V> for T where
V: MultiLane<T>,
impl<V, T> VZip<V> for T where
V: MultiLane<T>,
fn vzip(self) -> V
sourceimpl<T> WithSubscriber for T
impl<T> WithSubscriber for T
sourcefn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>ⓘNotable traits for WithDispatch<T>impl<T> Future for WithDispatch<T> where
T: Future, type Output = <T as Future>::Output;
where
S: Into<Dispatch>,
fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>ⓘNotable traits for WithDispatch<T>impl<T> Future for WithDispatch<T> where
T: Future, type Output = <T as Future>::Output;
where
S: Into<Dispatch>,
T: Future, type Output = <T as Future>::Output;
Attaches the provided Subscriber
to this type, returning a
WithDispatch
wrapper. Read more
sourcefn with_current_subscriber(self) -> WithDispatch<Self>ⓘNotable traits for WithDispatch<T>impl<T> Future for WithDispatch<T> where
T: Future, type Output = <T as Future>::Output;
fn with_current_subscriber(self) -> WithDispatch<Self>ⓘNotable traits for WithDispatch<T>impl<T> Future for WithDispatch<T> where
T: Future, type Output = <T as Future>::Output;
T: Future, type Output = <T as Future>::Output;
Attaches the current default Subscriber
to this type, returning a
WithDispatch
wrapper. Read more