std::cell::Cell - Rust
Description: API documentation for the Rust `Cell` struct in crate `std`.
Keywords: rust, rustlang, rust-lang, Cell

# Struct std::cell::Cell 1.0.0[−][src]

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

A mutable memory location.

# Examples

Here you can see how using `Cell<T>` allows to use mutable field inside immutable struct (which is also called '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, because my_struct is immutable
    // my_struct.regular_field = new_value;

    // WORKS, although `my_struct` is immutable, field `special_field` is mutable because it is Cell
    my_struct.special_field.set(new_value);
    assert_eq!(my_struct.special_field.get(), new_value);Run

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();Run

####

`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);Run

###

`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);Run

####

`pub fn set(&self, val: T)`

[src]

Sets the contained value.

# Examples

    use std::cell::Cell;

    let c = Cell::new(5);

    c.set(10);Run

####

`pub fn swap(&self, other: &Cell<T>)`

1.17.0
[src]

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

####

`pub fn replace(&self, val: T) -> T`

1.17.0
[src]

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);Run

####

`pub fn into_inner(self) -> T`

1.17.0
[src]

Unwraps the value.

# Examples

    use std::cell::Cell;

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

    assert_eq!(five, 5);Run

###

`impl<T> Cell<T> where T: ?Sized,`

[src]

####

`pub fn as_ptr(&self) -> *mut T`

1.12.0
[src]

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

####
ⓘImportant traits for &'a mut I

### Important traits for &'a mut I

`impl<'a, I> Iterator for &'a mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`

`pub fn get_mut(&mut self) -> &mut T`

1.11.0
[src]

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);Run

####

`pub fn from_mut(t: &mut T) -> &Cell<T>`

[src]

🔬 This is a nightly-only experimental API. (`as_cell` #43038)

Returns a `&Cell<T>` from a `&mut T`

# Examples

    #![feature(as_cell)]
    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

###

`impl<T> Cell<T> where T: Default,`

[src]

####

`pub fn take(&self) -> T`

1.17.0
[src]

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

###

`impl<T> Cell<[T]>`

[src]

####
ⓘImportant traits for &'a [u8]

### Important traits for &'a [u8]

`impl<'a> Read for &'a [u8]impl<'a> Write for &'a mut [u8]`

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

[src]

🔬 This is a nightly-only experimental API. (`as_cell` #43038)

Returns a `&[Cell<T>]` from a `&Cell<[T]>`

# Examples

    #![feature(as_cell)]
    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

## Trait Implementations

###

`impl<T> From<T> for Cell<T>`

1.12.0
[src]

####

`fn from(t: T) -> Cell<T>`

[src]

Performs the conversion.

###

`impl<T> Clone for Cell<T> where T: Copy,`

[src]

####

`fn clone(&self) -> Cell<T>`

[src]

Returns a copy of the value. Read more

####

`fn clone_from(&mut self, source: &Self)`

[src]

Performs copy-assignment from `source`. Read more

###

`impl<T> Debug for Cell<T> where T: Copy + Debug,`

[src]

####

`fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`

[src]

Formats the value using the given formatter. Read more

###

`impl<T> PartialOrd<Cell<T>> for Cell<T> where T: Copy + PartialOrd<T>,`

1.10.0
[src]

####

`fn partial_cmp(&self, other: &Cell<T>) -> Option<Ordering>`

[src]

This method returns an ordering between `self` and `other` values if one exists. Read more

####

`fn lt(&self, other: &Cell<T>) -> bool`

[src]

This method tests less than (for `self` and `other`) and is used by the `<` operator. Read more

####

`fn le(&self, other: &Cell<T>) -> bool`

[src]

This method tests less than or equal to (for `self` and `other`) and is used by the `<=` operator. Read more

####

`fn gt(&self, other: &Cell<T>) -> bool`

[src]

This method tests greater than (for `self` and `other`) and is used by the `>` operator. Read more

####

`fn ge(&self, other: &Cell<T>) -> bool`

[src]

This method tests greater than or equal to (for `self` and `other`) and is used by the `>=` operator. Read more

###

`impl<T> Ord for Cell<T> where T: Copy + Ord,`

1.10.0
[src]

####

`fn cmp(&self, other: &Cell<T>) -> Ordering`

[src]

This method returns an `Ordering` between `self` and `other`. Read more

####

`fn max(self, other: Self) -> Self`

1.21.0
[src]

Compares and returns the maximum of two values. Read more

####

`fn min(self, other: Self) -> Self`

1.21.0
[src]

Compares and returns the minimum of two values. Read more

###

`impl<T> Eq for Cell<T> where T: Copy + Eq,`

1.2.0
[src]

###

`impl<T> PartialEq<Cell<T>> for Cell<T> where T: Copy + PartialEq<T>,`

[src]

####

`fn eq(&self, other: &Cell<T>) -> bool`

[src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

####

`#[must_use] fn ne(&self, other: &Rhs) -> bool`

[src]

This method tests for `!=`.

###

`impl<T, U> CoerceUnsized<Cell<U>> for Cell<T> where T: CoerceUnsized<U>,`

[src]

###

`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> Send for Cell<T> where T: Send + ?Sized,`

[src]

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