title: Computed property from a promise
body: <p>I have a ember-data model with a relationship(many-many). So there is a computed property depends on the relationship element. I need to return boolean value based on data of the relationship property.</p>
  
  <pre><code>isAllowed: function(){
          return this.get('allowedUsers').then(function(data){
              var user = this.get('currentUser');
              return data.contains(user);
          }.bind(this));
  }.property()
  </code></pre>
  
  <p>In the above code, <code>isAllowed</code> is the computed property and <code>allowedUsers</code> is in many relation with <code>user</code> model and <code>async</code> is set as <code>true</code>. isAllowed is getting set to the promise object rather returned boolean. I even tried to create another promise object like below but no luck.</p>
  
  <pre><code> isAllowed: function(){
              return new Ember.RSVP.promise(function(resolve, reject){
                 this.get('allowedUsers').then(function(data){
                  var user = this.get('currentUser');
                   resolve(data.contains(user));
                }.bind(this));
  
              }.bind(this));
      }.property()
  </code></pre>
  
  <p>How can I make sure that isAllowed is set to boolean value rather the promise object?</p>