Struct async_once_cell::OnceFuture

pub struct OnceFuture<T, F = Box<dyn Future<Output = T> + Send>, I = Infallible> { /* fields omitted */ }

A Future which is executed exactly once, producing an output accessible without locking.

This is primarily used as a building block for Lazy and ConstLazy, but can be used on its own to produce more complex building blocks.

Implementations

impl<T, F, I> OnceFuture<T, F, I>

pub const fn with_init(init: I) -> Self

Creates a new OnceFuture with an initializing value

pub fn get(&self) -> Option<&T>

Gets the value without blocking or starting the initialization.

pub fn get_mut(&mut self) -> (Option<&mut I>, Option<&mut T>)

Get mutable access to the initializer or final value.

This requires mutable access to self, so rust’s aliasing rules prevent any concurrent access and allow violating the usual rules for accessing this cell.

pub fn into_inner(self) -> (Option<I>, Option<T>)

Gets the initializer or final value

impl<T, F> OnceFuture<T, F>

pub const fn new() -> Self

Creates a new OnceFuture without an initializing value

The resulting Future must be produced by the closure passed to get_or_init_with

impl<F> OnceFuture<F::Output, F> where
    F: Future + Send + 'static, 

pub fn from_future(future: F) -> Self

Creates a new OnceFuture directly from a Future.

The gen_future or init_future functions will never be called.

impl<T, F, I> OnceFuture<T, F, I> where
    F: Future<Output = T> + Send + 'static, 

pub async fn get_or_init_with(&self, gen_future: impl FnOnce() -> F) -> &T

Create and run the future until it produces a result, then return a reference to that result.

pub fn poll_init_with(
    &self,
    cx: &mut Context<'_>,
    gen_future: impl FnOnce() -> F
) -> Poll<&T>

Create and run the future until it produces a result, then return a reference to that result.

pub async fn get_or_populate_with(
    &self,
    into_future: impl FnOnce(Option<I>) -> F
) -> &T

Create and run the future until it produces a result, then return a reference to that result.

pub fn poll_populate(
    &self,
    cx: &mut Context<'_>,
    into_future: impl FnOnce(Option<I>) -> F
) -> Poll<&T>

Create and run the future until it produces a result, then return a reference to that result.

Trait Implementations

impl<T: RefUnwindSafe + UnwindSafe, F, I: RefUnwindSafe> RefUnwindSafe for OnceFuture<T, F, I>

impl<T: Send, F: Send, I: Send> Send for OnceFuture<T, F, I>

impl<T: Sync + Send, F: Send, I: Send> Sync for OnceFuture<T, F, I>

impl<T, F, I> Unpin for OnceFuture<T, F, I>

impl<T: UnwindSafe, F, I: UnwindSafe> UnwindSafe for OnceFuture<T, F, I>