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ember-concurrency tasks can be canceled either explicitly (by calling one of the cancel methods on a task or task instance) or implicitly (based on how the task is configured, or because the task's host object was destroyed).

Generally speaking, it is much better to configure your tasks properly (via Task Modifiers) such that they'll be implicitly/automatically canceled at the right time, but there are still some cases where explicit cancelation is the only option.

Explicit Cancelation

There are two ways to explicitly cancel a task:

  1. Call task.cancelAll() on the Task object — this will cancel all running or enqueued Task Instances for that task.
  2. Call taskInstance.cancel() on a Task Instance (the object returned from a prior call to task.perform())


Running tasks: 0

Tip: You can also use the .numRunning property to get the current number of running task instances for a given task, e.g. {{myTask.numRunning}}: 0

<h5>Running tasks: {{this.count}}</h5>

<button type="button" {{on "click" this.performTask}}>Perform Task</button>
{{#if this.count}}
  <button type="button" {{on "click" this.cancelAll}}>Cancel All</button>
{{#if this.mostRecent.isRunning}}
  <button type="button" {{on "click" this.cancelMostRecent}}>Cancel Most Recent</button>
export default class CancelationController extends Controller {
  count = 0;
  mostRecent = null;

  @task *myTask() {
    try {
      yield forever;
    } finally {
      // finally blocks always get called,
      // even when the task is being canceled

  performTask() {
    let task = this.myTask;
    let taskInstance = task.perform();
    this.set('mostRecent', taskInstance);

  cancelAll() {

  cancelMostRecent() {

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