ember-message-bus

Explore new patterns of event-driven communication with ember-message-bus. This addon adds a simple service to your application, message-bus, which you can use to facilitate loosely coupled communications between services, components, and other Ember objects.

Installation

ember install ember-message-bus

Usage

First, inject the message-bus service into your object:

import Ember from 'ember';

export default Ember.Component.extend({
  messageBus: Ember.inject.service('message-bus')
});

Once the message-bus has been injected, you can subscribe to events through it:

import Ember from 'ember';

export default Ember.Component.extend({
  messageBus: Ember.inject.service('message-bus'),

  init() {
    this._super(...arguments);

    this.get('messageBus').subscribe('my-event', this, this.doSomething);
  },

  doSomething(arg1, arg2) {
    console.log(arg1 + arg2);
  }
});

subscribe expects three arguments: 1) the name of the event, 2) the context, typically this, and 3) the callback.

Finally, you can publish events to trigger the subscription:

import Ember from 'ember';

export default Ember.Component.extend({
  messageBus: Ember.inject.service('message-bus'),

  action: {
    click() {
      this.get('messageBus').publish('my-event', 1, 2);
    }
  }
});

publish expects one or more arguments. The first argument must be the name of the event. After that, you can pass as many arguments as you like into publish. These arguments will be handed to the subscribing callback.

Testing

It's easy to test if a message is published. First, run initializeQUnitAssertions:

import { initializeQUnitAssertions } from 'ember-message-bus';

moduleForComponent('my-component', 'Integration | Component | my component', {
  integration: true,

  beforeEach() {
    const appInstance = getOwner(this);

    initializeQUnitAssertions(appInstance);
  }
});

If you'd like to ensure that events are published, use the Qunit assertion willPublish like so:

assert.willPublish('shouldBeTriggered', '`shouldBeTriggered` was triggered');
assert.willPublish('shouldReceiveArgs', ['foo', arg2], '`shouldReceiveArgs` received the correct args');
assert.willPublish('shouldCallback', (param1, param2) => return param2 === arg2, '`shouldCallback` tested with callback');

Note that if you want to test that args are published, the expected args should be passed in as an array. Alternatively, you can provide a callback that will receive the args as their params.

On the other end, if you want to confirm that a message was not published, you can use willNotPublish:

assert.willNotPublish('thisMessageShouldNotBePublished', '`thisMessageShouldNotBePublished` was not published');

Note that in both cases, these assertions should be made before the message is actually published. So in a component integration test:

const foo = { bar: 'baz' };

this.set('foo', foo);

assert.willPublish('shouldBeTriggered', [foo], '`shouldBeTriggered` was triggered');

this.render(hbs`{{my-component foo=foo}}`);