[][src]Struct spin::Once

pub struct Once<T> { /* fields omitted */ }

A synchronization primitive which can be used to run a one-time global initialization. Unlike its std equivalent, this is generalized so that the closure returns a value and it is stored. Once therefore acts something like a future, too.


use spin;

static START: spin::Once<()> = spin::Once::new();

START.call_once(|| {
    // run initialization here


impl<T> Once<T>[src]

pub const INIT: Self[src]

Initialization constant of Once.

pub const fn new() -> Once<T>[src]

Creates a new Once value.

pub fn call_once<'a, F>(&'a self, builder: F) -> &'a T where
    F: FnOnce() -> T, 

Performs an initialization routine once and only once. The given closure will be executed if this is the first time call_once has been called, and otherwise the routine will not be invoked.

This method will block the calling thread if another initialization routine is currently running.

When this function returns, it is guaranteed that some initialization has run and completed (it may not be the closure specified). The returned pointer will point to the result from the closure that was run.


use spin;

static INIT: spin::Once<usize> = spin::Once::new();

fn get_cached_val() -> usize {

fn expensive_computation() -> usize {
    // ...

pub fn try<'a>(&'a self) -> Option<&'a T>[src]

Returns a pointer iff the Once was previously initialized

pub fn wait<'a>(&'a self) -> Option<&'a T>[src]

Like try, but will spin if the Once is in the process of being initialized

Trait Implementations

impl<T: Debug> Debug for Once<T>[src]

impl<T: Send> Send for Once<T>[src]

impl<T: Send + Sync> Sync for Once<T>[src]

Auto Trait Implementations

impl<T> Unpin for Once<T> where
    T: Unpin

Blanket Implementations

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 

type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> Into<U> for T where
    U: From<T>, 

impl<T> From<T> for T[src]

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

impl<T> Borrow<T> for T where
    T: ?Sized

impl<T> BorrowMut<T> for T where
    T: ?Sized

impl<T> Any for T where
    T: 'static + ?Sized