Struct Cell 

pub struct Cell<T: ?Sized> { /* private fields */ }

A mutable memory location.

Memory layout

Cell<T> has the same memory layout and caveats as UnsafeCell<T>. In particular, this means that Cell<T> has the same in-memory representation as its inner type T.

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)

where T:,

Sets the contained value.

Examples

use std::cell::Cell;

let c = Cell::new(5);

c.set(10);

pub const 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);

impl<T: Copy> Cell<T>

pub const 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();

Trait Implementations

impl<T> Send for Cell<T>

where T: Send + ?Sized,

impl<T: ?Sized> !Sync for Cell<T>