Struct smol::Task

source · []
pub struct Task<T> { /* private fields */ }
Expand description

A spawned task.

A Task can be awaited to retrieve the output of its future.

Dropping a Task cancels it, which means its future won’t be polled again. To drop the Task handle without canceling it, use detach() instead. To cancel a task gracefully and wait until it is fully destroyed, use the cancel() method.

Note that canceling a task actually wakes it and reschedules one last time. Then, the executor can destroy the task by simply dropping its Runnable or by invoking run().

Examples

use smol::{future, Executor};
use std::thread;

let ex = Executor::new();

// Spawn a future onto the executor.
let task = ex.spawn(async {
    println!("Hello from a task!");
    1 + 2
});

// Run an executor thread.
thread::spawn(move || future::block_on(ex.run(future::pending::<()>())));

// Wait for the task's output.
assert_eq!(future::block_on(task), 3);

Implementations

Detaches the task to let it keep running in the background.

Examples
use smol::{Executor, Timer};
use std::time::Duration;

let ex = Executor::new();

// Spawn a deamon future.
ex.spawn(async {
    loop {
        println!("I'm a daemon task looping forever.");
        Timer::after(Duration::from_secs(1)).await;
    }
})
.detach();

Cancels the task and waits for it to stop running.

Returns the task’s output if it was completed just before it got canceled, or None if it didn’t complete.

While it’s possible to simply drop the Task to cancel it, this is a cleaner way of canceling because it also waits for the task to stop running.

Examples
use smol::{future, Executor, Timer};
use std::thread;
use std::time::Duration;

let ex = Executor::new();

// Spawn a deamon future.
let task = ex.spawn(async {
    loop {
        println!("Even though I'm in an infinite loop, you can still cancel me!");
        Timer::after(Duration::from_secs(1)).await;
    }
});

// Run an executor thread.
thread::spawn(move || future::block_on(ex.run(future::pending::<()>())));

future::block_on(async {
    Timer::after(Duration::from_secs(3)).await;
    task.cancel().await;
});

Converts this task into a FallibleTask.

Like Task, a fallible task will poll the task’s output until it is completed or cancelled due to its Runnable being dropped without being run. Resolves to the task’s output when completed, or None if it didn’t complete.

Examples
use smol::{future, Executor};
use std::thread;

let ex = Executor::new();

// Spawn a future onto the executor.
let task = ex.spawn(async {
    println!("Hello from a task!");
    1 + 2
})
.fallible();

// Run an executor thread.
thread::spawn(move || future::block_on(ex.run(future::pending::<()>())));

// Wait for the task's output.
assert_eq!(future::block_on(task), Some(3));
use smol::future;

// Schedule function which drops the runnable without running it.
let schedule = move |runnable| drop(runnable);

// Create a task with the future and the schedule function.
let (runnable, task) = async_task::spawn(async {
    println!("Hello from a task!");
    1 + 2
}, schedule);
runnable.schedule();

// Wait for the task's output.
assert_eq!(future::block_on(task.fallible()), None);

Returns true if the current task is finished.

Note that in a multithreaded environment, this task can change finish immediately after calling this function.

Trait Implementations

Formats the value using the given formatter. Read more

Executes the destructor for this type. Read more

The type of value produced on completion.

Attempt to resolve the future to a final value, registering the current task for wakeup if the value is not yet available. Read more

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Returns the argument unchanged.

A convenience for calling Future::poll() on !Unpin types.

Returns the result of self or other future, preferring self if both are ready. Read more

Returns the result of self or other future, with no preference if both are ready. Read more

Catches panics while polling the future. Read more

Boxes the future and changes its type to dyn Future + Send + 'a. Read more

Boxes the future and changes its type to dyn Future + 'a. Read more

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

🔬 This is a nightly-only experimental API. (into_future)

The output that the future will produce on completion.

🔬 This is a nightly-only experimental API. (into_future)

Which kind of future are we turning this into?

🔬 This is a nightly-only experimental API. (into_future)

Creates a future from a value.

The type returned in the event of a conversion error.

Performs the conversion.

The type of successful values yielded by this future

The type of failures yielded by this future

Poll this TryFuture as if it were a Future. Read more

The type returned in the event of a conversion error.

Performs the conversion.