Struct async_once_cell::Lazy

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pub struct Lazy<T, F> { /* private fields */ }

Expand description

A value which is computed on demand by running a future.

Unlike OnceCell, if a task is cancelled, the initializing future’s execution will be continued by other (concurrent or future) callers of Lazy::get.

use std::sync::Arc;
use async_once_cell::Lazy;

struct Data {
    id: u32,
}

let shared = Arc::pin(Lazy::new(async move {
    Data { id: 4 }
}));

assert_eq!(shared.as_ref().get().await.id, 4);

Implementations§

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impl<T, F> Lazy<T, F>where F: Future<Output = T>,

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pub const fn new(future: F) -> Self

Creates a new lazy value with the given initializing future.

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pub async fn get(self: Pin<&Self>) -> Pin<&T>

Forces the evaluation of this lazy value and returns a reference to the result.

The Pin::static_ref function may be useful if this is a static value.

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impl<T, F> Lazy<T, F>where F: Future<Output = T> + Unpin,

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pub async fn get_unpin(&self) -> &T

Forces the evaluation of this lazy value and returns a reference to the result.

Unlike Self::get, this does not require pinning the object.

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impl<T, F> Lazy<T, F>

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pub const fn from_future(future: F) -> Self

Creates a new lazy value with the given initializing future.

This is equivalent to Self::new but with no type bound.

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pub const fn with_value(value: T) -> Self

Creates an already-initialized lazy value.

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

Gets the value without blocking or starting the initialization.

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pub fn try_get_mut(self: Pin<&mut Self>) -> Option<Pin<&mut T>>

Gets the value without blocking or starting the initialization.

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.

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

Gets the value without blocking or starting the initialization.

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.

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