Ember: How to get computed properties from a nested model? - ember.js

Question

First: I have no idea how to work with promises in Ember.js.
I want to call a property of my controller which depends on async model-data which is also nested.
Also, my model looks something like that:
+-------------+         +------------+
| Method      | hasMany |  Practice  |
|             +--------->            |
|             |         |            |
+-------------+         +------------+
                              |       
                              | hasMany
                        +-----v------+
                        | Alpha      |
                        |            |
                        |            |
                        +------------+
So I created something like this:
allAlphas: function() {
var self = this;
var returnValue = "nichts";
var promises = {
allAlphas: self.get('model.method').then(function(method) {
//get the practices
return method.get('practices');
}).then(function(practices) {
//get the alphaSField in EVERY practice
//the alphasField is the (hasmany 'alpha')member in practice
var alphasFields = practices.getEach('alphas');
return Ember.RSVP.all(alphasFields).then(function() {
return alphasFields;
});
}).then(function(alphasFields) {
// here: get all the alphas via promise or something
})
};
Ember.RSVP.hash(promises).then(function(results) {
// return all the alphas (of all pracitces in the method) in some way
});
}.property()
There are two Problems (like already metioned in the comments):
How to load nested hasMany async models like all alphas in all practices.
How to return the complete result as a property in the RSVP.hash-Method for use in templates or something
Can anybody help me?
Edit 06/20/2015
As #Kingpin2k suggested, Ive added a Gist for better understanding of my Problem:
https://gist.github.com/MarcManhart/e5c1d91e8fdfd876de37

Answer 1

just return an array, and populate the array after the fact.
allAlphas: function() {
var self = this,
returnValue = [];
this.get('model.method').then(function(method) {
//get the practices
return method.get('practices');
}).then(function(practices) {
//get the alphasField in EVERY practice
//the alphasField is the (hasmany 'alpha')member in practice
var alphas= practices.getEach('alphas');
Ember.RSVP.all(alphas).then(function(resolvedAlphas) {
resolvedAlphas.forEach(function(afs){
returnValue.pushObjects(afs.toArray());
});
});
});
return returnValue;
}.property()
Update
It looks like pushObjects doesn't like the ED Collection (or maybe it doesn't like the promises underneath, I didn't look into it that much). Also we should use the resolved values instead of the promises sent in (alphas vs resolvedAlphas in my code below).
Example: http://emberjs.jsbin.com/cinobetoyu/1/edit?js,output