Struct std::cell::Cell
#[repr(transparent)]pub struct Cell<T> where T: ?Sized, { /* fields omitted */ }
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
impl<T> Cell<T>
pub const fn new(value: T) -> Cell<T>
Creates a new Cell
containing the given value.
Examples
use std::cell::Cell; let c = Cell::new(5);
pub fn set(&self, val: T)
Sets the contained value.
Examples
use std::cell::Cell; let c = Cell::new(5); c.set(10);
pub fn swap(&self, other: &Cell<T>)
Swaps the values of two Cells. 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());
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);
Unwraps the value.
Examples
use std::cell::Cell; let c = Cell::new(5); let five = c.into_inner(); assert_eq!(five, 5);
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();
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);
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();
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);
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);
pub fn take(&self) -> T
Takes the value of the cell, leaving Default::default()
in its place.
Examples
use std::cell::Cell; let c = Cell::new(5); let five = c.take(); assert_eq!(five, 5); assert_eq!(c.into_inner(), 0);
impl<T> 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);
impl<T, const N: usize> Cell<[T; N]>
pub fn as_array_of_cells(&self) -> &[Cell<T>; N]
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
pub fn clone(&self) -> Cell<T>
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)
Performs copy-assignment from source
. Read more
pub fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>
Formats the value using the given formatter. Read more
pub fn default() -> Cell<T>
Creates a Cell<T>
, with the Default
value for T.
impl<T> From<T> for Cell<T>
pub fn from(t: T) -> Cell<T>
Performs the conversion.
pub fn cmp(&self, other: &Cell<T>) -> Ordering
fn max(self, other: Self) -> Self
Compares and returns the maximum of two values. Read more
fn min(self, other: Self) -> Self
Compares and returns the minimum of two values. Read more
fn clamp(self, min: Self, max: Self) -> Self
Restrict a value to a certain interval. Read more
pub fn eq(&self, other: &Cell<T>) -> bool
This method tests for self
and other
values to be equal, and is used by ==
. Read more
fn ne(&self, other: &Rhs) -> bool
This method tests for !=
.
impl<T> PartialOrd<Cell<T>> for Cell<T> where
T: PartialOrd<T> + Copy,
pub fn partial_cmp(&self, other: &Cell<T>) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
pub fn lt(&self, other: &Cell<T>) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
pub 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
pub fn gt(&self, other: &Cell<T>) -> bool
This method tests greater than (for self
and other
) and is used by the >
operator. Read more
pub fn ge(&self, other: &Cell<T>) -> bool
This method tests greater than or equal to (for self
and other
) and is used by the >=
operator. Read more
impl<T, U> CoerceUnsized<Cell<U>> for Cell<T> where
T: CoerceUnsized<U>,
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
impl<T> From<!> for T
pub fn from(t: !) -> T
Performs the conversion.
impl<T> From<T> for T
pub fn from(t: T) -> T
Performs the conversion.
pub fn into(self) -> U
Performs the conversion.
type Owned = T
The resulting type after obtaining ownership.
pub fn to_owned(&self) -> T
Creates owned data from borrowed data, usually by cloning. Read more
pub fn clone_into(&self, target: &mut T)
toowned_clone_into
#41263)recently added
Uses borrowed data to replace owned data, usually by cloning. Read more
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.Cell.html