Bevy Async Task provides Bevy system parameters to run asyncronous tasks in the background with timeout support and future output in the same system. It also provides syntactic sugar to reduce boiler plate when blocking on futures within synchronous contexts.

Bevy version support

Usage

There are several examples for reference.

You can also run examples on web:

# Make sure the Rust toolchain supports the wasm32 target
rustup target add wasm32-unknown-unknown

cargo run_wasm --example simple

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() {
        AsyncTaskStatus::Idle => {
            task_executor.start(long_task());
            info!("Started new task!");
        }
        AsyncTaskStatus::Pending => {
            // <Insert loading screen>
        }
        AsnycTaskStatus::Finished(v) => {
            info!("Received {v}");
        }
    }
}

Poll many similar tasks simultaneously with AsyncTaskPool<T>:

fn my_system(mut task_pool: AsyncTaskPool<u64>) {
    if task_pool.is_idle() {
        info!("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 {
            info!("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);

Community

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Contributions are welcome by pull request. The Rust code of conduct applies.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.