Cell in std::cell - Rust (original) (raw)
Struct Cell
1.0.0 · Source
pub struct Cell<T>
where
T: ?Sized,
{ /* private fields */ }Expand description
A mutable memory location.
§Memory layout
Cell<T> has the same memory layout and caveats asUnsafeCell. In particular, this means thatCell<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.
1.0.0 (const: 1.24.0) · Source
Creates a new Cell containing the given value.
§Examples
use std::cell::Cell;
let c = Cell::new(5);1.0.0 · Source
Sets the contained value.
§Examples
use std::cell::Cell;
let c = Cell::new(5);
c.set(10);1.17.0 · Source
Swaps the values of two Cells.
The difference with std::mem::swap is that this function doesn’t require a &mut reference.
§Panics
This function will panic if self and other are different Cells that partially overlap. (Using just standard library methods, it is impossible to create such partially overlapping Cells. However, unsafe code is allowed to e.g. create two &Cell<[i32; 2]> that partially overlap.)
§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 (const: unstable) · Source
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: 1.83.0) · Source
Unwraps the value, consuming the cell.
§Examples
use std::cell::Cell;
let c = Cell::new(5);
let five = c.into_inner();
assert_eq!(five, 5);1.0.0 (const: unstable) · Source
Returns a copy of the contained value.
§Examples
use std::cell::Cell;
let c = Cell::new(5);
let five = c.get();🔬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);1.12.0 (const: 1.32.0) · Source
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 (const: unstable) · Source
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 (const: unstable) · Source
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);1.17.0 · Source
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);1.37.0 (const: unstable) · Source
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);🔬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();Creates a Cell<T>, with the Default value for T.
Creates a new Cell<T> containing the given value.
Tests for self and other values to be equal, and is used by ==.
Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
This method returns an ordering between self and other values if one exists. Read more
Tests less than (for self and other) and is used by the < operator. Read more
Tests less than or equal to (for self and other) and is used by the<= operator. Read more
Tests greater than (for self and other) and is used by the >operator. Read more
Tests greater than or equal to (for self and other) and is used by the >= operator. Read more