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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.

Methods

impl<T> Cell<T> where
    T: Copy, [src]

pub fn get(&self) -> T[src]

Returns a copy of the contained value.

Examples

use std::cell::Cell;

let c = Cell::new(5);

let five = c.get();

pub fn update<F>(&self, f: F) -> T where
    F: FnOnce(T) -> T, [src]

🔬 This is a nightly-only experimental API. (cell_update #50186)

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);

impl<T> Cell<T>[src]

pub const fn new(value: T) -> Cell<T>[src]

Creates a new Cell containing the given value.

Examples

use std::cell::Cell;

let c = Cell::new(5);

pub fn set(&self, val: T)[src]

Sets the contained value.

Examples

use std::cell::Cell;

let c = Cell::new(5);

c.set(10);

pub fn swap(&self, other: &Cell<T>)[src]1.17.0

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[src]1.17.0

Replaces the contained value, and returns it.

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);

pub fn into_inner(self) -> T[src]1.17.0

Unwraps the value.

Examples

use std::cell::Cell;

let c = Cell::new(5);
let five = c.into_inner();

assert_eq!(five, 5);

impl<T> Cell<T> where
    T: ?Sized, [src]

pub const fn as_ptr(&self) -> *mut T[src]1.12.0

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[src]1.11.0

ⓘImportant traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized, 
    type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized, 
    type Item = <I as Iterator>::Item;
impl<'_, R: Read + ?Sized> Read for &'_ mut R
impl<'_, W: Write + ?Sized> Write for &'_ mut W

Returns a mutable reference to the underlying data.

This call borrows Cell mutably (at compile-time) which guarantees that we possess the only reference.

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>[src]1.37.0

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);

impl<T> Cell<T> where
    T: Default, [src]

pub fn take(&self) -> T[src]1.17.0

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]>[src]

pub fn as_slice_of_cells(&self) -> &[Cell<T>][src]1.37.0

ⓘImportant traits for &'_ [u8]
impl<'_> Read for &'_ [u8]
impl<'_> Write for &'_ mut [u8]

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);

Trait Implementations

impl<T> !Sync for Cell<T> where
    T: ?Sized, [src]

impl<T> Default for Cell<T> where
    T: Default, [src]

fn default() -> Cell<T>[src]

Creates a Cell<T>, with the Default value for T.

impl<T> Clone for Cell<T> where
    T: Copy, [src]

fn clone_from(&mut self, source: &Self)[src]

Performs copy-assignment from source. Read more

impl<T> Eq for Cell<T> where
    T: Copy + Eq, [src]1.2.0

impl<T> PartialOrd<Cell<T>> for Cell<T> where
    T: Copy + PartialOrd<T>, [src]1.10.0

impl<T> Ord for Cell<T> where
    T: Copy + Ord, [src]1.10.0

fn max(self, other: Self) -> Self[src]1.21.0

Compares and returns the maximum of two values. Read more

fn min(self, other: Self) -> Self[src]1.21.0

Compares and returns the minimum of two values. Read more

fn clamp(self, min: Self, max: Self) -> Self[src]

🔬 This is a nightly-only experimental API. (clamp #44095)

Restrict a value to a certain interval. Read more

impl<T> Debug for Cell<T> where
    T: Copy + Debug, [src]

impl<T> PartialEq<Cell<T>> for Cell<T> where
    T: Copy + PartialEq<T>, [src]

fn ne(&self, other: &Rhs) -> bool[src]

This method tests for !=.

impl<T> Send for Cell<T> where
    T: Send + ?Sized, [src]

impl<T, U> CoerceUnsized<Cell<U>> for Cell<T> where
    T: CoerceUnsized<U>, [src]

impl<T> From<T> for Cell<T>[src]1.12.0

Auto Trait Implementations

impl<T: ?Sized> UnwindSafe for Cell<T> where
    T: UnwindSafe, 

impl<T> !RefUnwindSafe for Cell<T>

impl<T: ?Sized> Unpin for Cell<T> where
    T: Unpin, 

Blanket Implementations

impl<T, U> TryFrom<U> for T where
    U: Into<T>, [src]

type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> Into<U> for T where
    U: From<T>, [src]

impl<T> From<T> for T[src]

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, [src]

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

impl<T> Borrow<T> for T where
    T: ?Sized, [src]

ⓘImportant traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized, 
    type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized, 
    type Item = <I as Iterator>::Item;
impl<'_, R: Read + ?Sized> Read for &'_ mut R
impl<'_, W: Write + ?Sized> Write for &'_ mut W

impl<T> BorrowMut<T> for T where
    T: ?Sized, [src]

ⓘImportant traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized, 
    type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized, 
    type Item = <I as Iterator>::Item;
impl<'_, R: Read + ?Sized> Read for &'_ mut R
impl<'_, W: Write + ?Sized> Write for &'_ mut W

impl<T> Any for T where
    T: 'static + ?Sized, [src]

impl<T> ToOwned for T where
    T: Clone, [src]

type Owned = T

The resulting type after obtaining ownership.

© 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