Struct TakeStatic 

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

A synchronization primitive which can be accessed only once.

This type is a thread-safe cell that can only be used in statics. TakeStatic::take provides a mutable reference to the contents without RAII guards, but only on the first try.

Similarities with takecell::TakeCell

TakeStatic is similar to takecell::TakeCell in that both can be used to create singletons. Additionally, TakeCells can be created at runtime, making them suitable for other use-cases such as doing work only once. TakeStatic, on the other hand, is specialized to creating statics through take_static, allowing even !Send types to be used and not requiring explicitly naming the wrapper type.

Similarities with cortex_m::singleton

TakeStatic can be used similarly to cortex_m::singleton to create a mutable reference to a statically allocated value. In contrast to cortex_m::singleton, TakeStatic is thread safe.

Examples

use take_static::take_static;

take_static! {
    static NUMBER: usize = 5;
}

assert_eq!(NUMBER.take(), Some(&mut 5));
assert_eq!(NUMBER.take(), None);

Implementations

impl<T: ?Sized> TakeStatic<T>

pub fn take(&self) -> Option<&mut T>

Takes the mutable reference to the wrapped value.

Only the first call returns Some. All subsequent calls return None.

Examples

use take_static::take_static;

take_static! {
    static TAKE_STATIC: usize = 5;
}

let number = TAKE_STATIC.take().unwrap();
assert_eq!(number, &mut 5);
assert!(TAKE_STATIC.take().is_none());

pub fn is_taken(&self) -> bool

Returns true if the mutable reference has been taken.

Examples

use take_static::take_static;

take_static! {
    static TAKE_STATIC: usize = 5;
}

assert!(!TAKE_STATIC.is_taken());
let number = TAKE_STATIC.take().unwrap();
assert!(TAKE_STATIC.is_taken());

Trait Implementations

impl<T: ?Sized> Debug for TakeStatic<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: ?Sized> Sync for TakeStatic<T>