blob: c8970c85052fa911242df10097027099bc173129 [file] [log] [blame]
use futures_core::task::Spawn;
mod spawn_error;
pub use self::spawn_error::SpawnError;
if_std! {
use futures_core::future::Future;
mod spawn_with_handle;
use self::spawn_with_handle::spawn_with_handle;
pub use self::spawn_with_handle::JoinHandle;
}
impl<Sp: ?Sized> SpawnExt for Sp where Sp: Spawn {}
/// Extension trait for `Spawn`
pub trait SpawnExt: Spawn {
/// Spawns a task that polls the given future with output `()` to
/// completion.
///
/// This method returns a [`Result`] that contains a [`SpawnError`] if
/// spawning fails.
///
/// You can use [`spawn_with_handle`](SpawnExt::spawn_with_handle) if
/// you want to spawn a future with output other than `()` or if you want
/// to be able to await its completion.
///
/// Note this method will eventually be replaced with the upcoming
/// `Spawn::spawn` method which will take a `dyn Future` as input.
/// Technical limitations prevent `Spawn::spawn` from being implemented
/// today. Feel free to use this method in the meantime.
///
/// ```
/// #![feature(async_await, await_macro, futures_api)]
/// # futures::executor::block_on(async {
/// use futures::executor::ThreadPool;
/// use futures::task::SpawnExt;
///
/// let mut executor = ThreadPool::new().unwrap();
///
/// let future = async { /* ... */ };
/// executor.spawn(future).unwrap();
/// # });
/// ```
#[cfg(feature = "std")]
fn spawn<Fut>(&mut self, future: Fut) -> Result<(), SpawnError>
where Fut: Future<Output = ()> + Send + 'static,
{
let res = self.spawn_obj(Box::new(future).into());
res.map_err(|err| SpawnError { kind: err.kind })
}
/// Spawns a task that polls the given future to completion and returns a
/// future that resolves to the spawned future's output.
///
/// This method returns a [`Result`] that contains a [`JoinHandle`], or, if
/// spawning fails, a [`SpawnError`]. [`JoinHandle`] is a future that
/// resolves to the output of the spawned future.
///
/// ```
/// #![feature(async_await, await_macro, futures_api)]
/// # futures::executor::block_on(async {
/// use futures::executor::ThreadPool;
/// use futures::future;
/// use futures::task::SpawnExt;
///
/// let mut executor = ThreadPool::new().unwrap();
///
/// let future = future::ready(1);
/// let join_handle = executor.spawn_with_handle(future).unwrap();
/// assert_eq!(await!(join_handle), 1);
/// # });
/// ```
#[cfg(feature = "std")]
fn spawn_with_handle<Fut>(
&mut self,
future: Fut
) -> Result<JoinHandle<Fut::Output>, SpawnError>
where Fut: Future + Send + 'static,
Fut::Output: Send,
{
spawn_with_handle(self, future)
}
}