#59 Ember Concurrency

Tip

Idea submitted by both Devin Weaver and Austin Burdine.
Tip by Devin Weaver
An alternative community de facto standard is an addon called ember-concurrency that makes a lot of the promise confusion go away.
It can be installed with the command ember install ember-concurrency.
Pros
Intuitive reasoning of complex asynchronous code.
Offers a complete API for managing tasks.
Can be canceled.
Can be used directly in a component without the need of a proxy object.
Destructures promises inside the task function.
Can use JavaScript try / catch / finally blocks to manage asynchronous assignment, exceptions, and cleanup.
Tasks are automagically cancelled on willDestroy event, avoiding errors setting values on destroyed objects (e.g. after a timer)
Cons
Not builtin – requires ember install ember-concurrency
Uses generator functions that can confuse developers used to promise chains.
JavaScript

 Ember from 'ember';
import { task, timeout } from 'ember-concurrency';
const { Component, set } = Ember;
export default Component.extend({
&nbsp; myTask: task(function * () {
 &nbsp; set(this, 'error', null);
 &nbsp; try {
&nbsp; &nbsp; yield timeout(2000);
 &nbsp; return 'Foobar';
 &nbsp; } catch (err) {
 &nbsp; set(this, 'error', error);
 &nbsp; }
&nbsp; }).keepLatest()
});

Ember from 'ember';

import { task, timeout } from 'ember-concurrency';

const { Component, set } = Ember;

export default Component.extend({

  myTask: task(function * () {

  set(this, 'error', null);

  try {

    yield timeout(2000);

  return 'Foobar';

  } catch (err) {

  set(this, 'error', error);

  }

  }).keepLatest()

});

Template

{{#if myTask.isIdle}}
 &lt;button onclick={{perform myTask}}&gt;
 &nbsp; Start Task
 &lt;/button&gt;
{{else}}
&nbsp; Loading&amp;hellip;
{{/if}}
{{#if myTask.last.value}}
 Done. {{myTask.last.value}}
{{/if}}
{{#if error}}
 Something went wrong. {{error}}
{{/if}}

  Start Task

</button>

  Loading&hellip;

Done. {{myTask.last.value}}

Something went wrong. {{error}}

Credits & Links

Thanks to Austin for the idea and Devin for write up.
ember-concurrency athttp://ember-concurrency.com/#/docs(good documentation, video and examples)
Related:tip #54

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#59 Ember Concurrency

Tip

Credits & Links

Free Programming Books and lifetime access to IconApp.io

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Published by

Emad Ibrahim