Implemented #172 with promises

[mbektimirov]

App.start now returns a promise which depends on all application widgets promisses. Just return a promise() in widget 'initialize' method to handle async loading. Sample code is bellow.

// test widget
define(function() {
  return {
    initialize: function() {
      var dfd = this.sandbox.data.deferred();

      this.html('I am a test');

      setTimeout(function () {
        dfd.resolve();
      }, 3000);

      return dfd.promise();
    }
  };
});

// main app
require(['lib/aura'], function(Aura) {
  Aura({ debug: { enable: true } }).start({ widgets: 'body' }).then(function() {
    // this callback will be called after test widget 
    // deferred object will resolved (after 3000 ms)
    console.warn("Aura app started !");
  });
});

[addyosmani]

Thanks for this change, @mbektimirov. Would it be possible to also add some docs (addition to the readme) covering this change?

[sbellity]

Thanks @mbektimirov ill try to review it today
An you also update the tests ? They seem to be failing on Travis

One comment though I went through the code quickly and my first thought is that we could probably do it in a more generic way by emitting events whenever all the widgets started via a Widget.startAll call have finished initialization...

[rspindel]

@sbellity +1 on using events over promises. See this good article debating their different strengths within asynchronous architecture and also my recent comment on using the Finite State Machine pattern on synchronizing events. http://www.joezimjs.com/javascript/javascript-asynchronous-architectures-events-vs-promises/

[addyosmani]

my first thought is that we could probably do it in a more generic way by emitting events whenever all the widgets started via a Widget.startAll call have finished initialization

I agree with this. @mbektimirov just pinging you again in case you have time to update the tests. This would be hugely appreciated.

[mbektimirov]

I remember about tests, still in vacation, sorry for delay. I'll fix this in about 3-4 days.

[addyosmani]

ping @mbektimirov in case you have time :)

[addyosmani]

@sbellity for our next release, do you feel this is important enough to write the tests ourselves and make it more generic then land? If not, we can certainly hold off on it.