async-lazy

An async version of once_cell::sync::Lazy, std::sync::OnceLock or lazy_static. Uses tokio's sychronization primitives.

This crate offers an API similar to the Lazy type from async-once-cell crate. The difference is that this crate's Lazy accepts an FnOnce() -> impl Future instead of a Future, which makes use in statics easier.

Crate features

• parking_lot: Enables the corresponding feature in tokio, and allows constructing Lazys in const contexts.
• nightly: Uses nightly Rust features to implement IntoFuture for references to Lazys, obviating the need to call force().

Example

use std::time::Duration;
use async_lazy::Lazy;

async fn some_computation() -> u32 {
    tokio::time::sleep(Duration::from_secs(1)).await;
    1 + 1
}

static LAZY : Lazy<u32> = Lazy::const_new(|| Box::pin(async { some_computation().await }));

#[tokio::main]
async fn main() {
    let result = tokio::spawn(async {
        *LAZY.force().await
    }).await.unwrap();

    assert_eq!(result, 2);
}