team.js

import Ember from 'ember';
import DS    from 'ember-data';

var computed = Ember.computed;
var get      = Ember.get;
var RSVP     = Ember.RSVP;

export default DS.Model.extend({
  name:    DS.attr('string'),
  players: DS.hasMany('player', { async: true }),
  coach:   DS.belongsTo('coach', { async: true }),
  
  coachScore: computed.alias('coach.score'),
  
  playersScore: computed('[email protected]', function() {
    var promise = get(this, 'players')
    .then(function(players) {
      return RSVP.all(players.mapBy('score'))
    })
    .then(function(scores) {
      return scores.reduce(function(previous, current) {
        return previous + current;
      }, []);
    });
    return DS.PromiseObject.create({ promise: promise });
  }),
  
  score: computed('playersScore', 'coachScore', function() {
    var playersScore = get(this, 'playersScore');
    var coachScore   = get(this, 'coachScore');
    
    return playersScore * coachScore;
  })
})