Struct core::cell::Cell1.0.0[−][src]

#[repr(transparent)]
pub struct Cell<T: ?Sized> { /* fields omitted */ }

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);

Run

See the module-level documentation for more.

Implementations

[src]

impl<T> Cell<T>

1.0.0 (const: 1.24.0)[src]

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);

Run

[src]

pub fn set(&self, val: T)

Sets the contained value.

Examples

use std::cell::Cell;

let c = Cell::new(5);

c.set(10);

Run

1.17.0[src]

pub fn swap(&self, other: &Self)

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());

Run

1.17.0[src]

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);

Run

1.17.0 (const: unstable)[src]

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);

Run

[src]

impl<T: Copy> Cell<T>

[src]

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();

Run

[src]

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

🔬 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);

Run

[src]

impl<T: ?Sized> Cell<T>

1.12.0 (const: 1.32.0)[src]

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();

Run

1.11.0[src]

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);

Run

1.37.0[src]

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);

Run

[src]

impl<T: Default> Cell<T>

1.17.0[src]

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);

Run

[src]

impl<T> Cell<[T]>

1.37.0[src]

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);

Run

[src]

impl<T, const N: usize> Cell<[T; N]>

[src]

pub fn as_array_of_cells(&self) -> &[Cell<T>; N]

🔬 This is a nightly-only experimental API. (as_array_of_cells #88248)

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();