ember-concurrency-result

Proof-of-concept of a Rust-ish Result return modifier for ember-concurrency tasks, based on an idea Alex Machtneer floated in the Ember Community Discord.

Some of this will probably changed.

Uses Result from true-myth.

Compatibility

Ember.js v2.18 or above
Ember CLI v2.13 or above
Node.js v8 or above
ember-concurrency 0.7.19 or above

Installation

ember install ember-concurrency-result

Usage

via wrapping of `task`

ember-concurrency-result adds a result function which can wrap an ember-concurrency TaskProperty. You can use the addon via this wrapping strategy like below:

// components/flaky-component.js
import Component from '@ember/component';
import { task } from 'ember-concurrency';
import { result } from 'ember-concurrency-result';
import getWidgetsFromFlakyApi from '../utils/get-widgets';
import UnavailableError from '../utils/errors/unavailable';

export default Component.extend({
  myTask: result(task(function*() {
    return yield getWidgetsFromFlakyApi();
  })),

  someMethod() {
    const lastValue = this.myTask.last.value;

    if (lastValue.isOk()) {
      const widgets = lastValue.value;

      alert(`There are ${widgets.length} widgets in the widgetry.`);
    } else if (lastValue.error instanceof UnavailableError) {
      alert("Those darn flaky APIs! They're at it again!");
    } else {
      alert('wtf.');
    }
  }
});

via `task` property modifier

The wrapping method above may not look as aesthetically pleasing, so instead, you may also add a .result modifier to ember-concurrency tasks through the magic of reaching into private APIs! ember-concurrency-result provides a defineModifier function that can be used somewhere early in the boot process, such as app.js or in an initializer, which will add a result modifier method to the TaskProperty prototype.

// app.js
import defineModifier from 'ember-concurrency-result/define-modifier';

defineModifier();

// remainder of app.js...

// components/flaky-component.js
import Component from '@ember/component';
import { task } from 'ember-concurrency';
import { result } from 'ember-concurrency-result';
import getWidgetsFromFlakyApi from '../utils/get-widgets';
import UnavailableError from '../utils/errors/unavailable';

export default Component.extend({
  myTask: task(function*() {
    return yield getWidgetsFromFlakyApi();
  }).result(),

  someMethod() {
    const lastValue = this.myTask.last.value;

    if (lastValue.isOk()) {
      const widgets = lastValue.value;

      alert(`There are ${widgets.length} widgets in the widgetry.`);
    } else if (lastValue.error instanceof UnavailableError) {
      alert("Those darn flaky APIs! They're at it again!");
    } else {
      alert('wtf.');
    }
  }
});

Because this relies on accessing ember-concurrency's TaskProperty intimate API and modifying the prototype for that object, it's not strictly recommended, but should be relatively safe to do, as the chances of that API changing drastically without a suitable replacement is unlikely.