vectorgameexperts / bevy-async-task

Ergonomic abstractions to async programming in Bevy for all platforms.

Bevy Async Task

A minimum crate for ergonomic abstractions to async programming in Bevy for all platforms. This crate helps to run async tasks in the background with timeout support and retrieve results in the same system, and helps to block on futures within synchronous contexts.

There is full API support for wasm and native. Android and iOS are untested (Help needed).

Bevy version support

bevy	bevy-async-task
0.12	1.3, main
0.11	1.2
<= 0.10	Unsupported

Usage

Please see examples for more.

Polling in systems

Poll one task at a time with AsyncTaskRunner<T>:

async fn long_task() -> u32 {
    sleep(Duration::from_millis(1000)).await;
    5
}

fn my_system(mut task_executor: AsyncTaskRunner<u32>) {
    match task_executor.poll() {
        AsnycTaskStatus::Idle => {
            task_executor.begin(long_task());
            println!("Started new task!");
        }
        AsnycTaskStatus::Pending => {
            // <Insert loading screen>
        }
        AsnycTaskStatus::Finished(v) => {
            println!("Received {v}");
        }
    }
}

Poll many similar tasks simultaneously with AsyncTaskPool<T>:

fn my_system(mut task_pool: AsyncTaskPool<u64>) {
    if task_pool.is_idle() {
        println!("Queueing 5 tasks...");
        for i in 1..=5 {
            task_pool.spawn(async move { // Closures work too!
                sleep(Duration::from_millis(i * 1000)).await;
                i
            });
        }
    }

    for status in task_pool.iter_poll() {
        if let AsyncTaskStatus::Finished(t) = status {
            println!("Received {t}");
        }
    }
}

Also, you may use timeouts or block on an AsyncTask<T>:

// Blocking:
let task = AsyncTask::new(async { 5 });
assert_eq!(5, task.blocking_recv());

// Timeout:
let task = AsyncTask::<()>::pending().with_timeout(Duration::from_millis(10));
assert!(task.blocking_recv().is_err());

Need to steer manually? Break the task into parts.

let task = AsyncTask::new(async move {
    sleep(Duration::from_millis(1000)).await;
    5
});
// Break the task into a runnable future and a receiver
let (fut, mut rx) = task.into_parts();
// The receiver will always be `None` until it is polled by Bevy.
assert_eq!(None, rx.try_recv());
// Run the future
let task_pool = bevy::prelude::AsyncComputeTaskPool::get();
let task = task_pool.spawn(fut);
task.detach(); // Forget and run in background
// Spin-lock, waiting for the result
let result = loop {
    if let Some(v) = rx.try_recv() {
        break v;
    }
};
assert_eq!(5, result);

License

This project is dual-licensed under both Apache 2.0 and MIT licenses.