Struct Group 

pub struct Group<E> { /* private fields */ }

A group of concurrent tasks that propagates the first error.

Create a new group with Group::new, spawn tasks with spawn or try_spawn, and collect results with wait.

Implementations

impl<E> Group<E>

where E: Send + 'static,

pub fn new() -> Self

Creates a new Group with no concurrency limit.

pub fn set_limit(&mut self, n: usize)

Limits the number of tasks that may run concurrently to at most n.

A limit of 0 prevents any new task from running. A negative value would indicate no limit, but since this is usize, no limit is the default (created by new).

Panics

Must not be called while any tasks are active.

impl<E> Group<E>

where E: Send + 'static,

pub fn spawn<F, Fut>(&self, f: F)

where F: FnOnce() -> Fut + Send + 'static, Fut: Future<Output = Result<(), E>> + Send + 'static,

Spawns a new task.

If a concurrency limit was set with set_limit and the maximum number of tasks is already running, the newly spawned task will block inside itself (not the caller) until a slot opens up.

This method returns immediately and never blocks the caller.

Panics

The task must not panic. See the crate-level docs.

pub fn try_spawn<F, Fut>(&self, f: F) -> bool

where F: FnOnce() -> Fut + Send + 'static, Fut: Future<Output = Result<(), E>> + Send + 'static,

Tries to spawn a new task without waiting for a concurrency slot.

If a limit is set and the maximum number of tasks is running, returns false without spawning the task. Otherwise spawns the task and returns true.

If no limit was set, this is equivalent to spawn and always returns true.

impl<E> Group<E>

where E: Send + 'static,

pub async fn wait(self) -> Result<(), E>

Waits for all spawned tasks to complete.

Returns the first error encountered, or Ok(()) if all tasks succeeded.

Consumes the group — no more tasks can be spawned after calling this.

Trait Implementations

impl<E> Default for Group<E>

where E: Send + 'static,

fn default() -> Self

Returns the “default value” for a type.