Computed property with promise not working

computed_property_with_promise_not_working.js

import Ember from 'ember';

var PromiseObject = Ember.ObjectProxy.extend(Ember.PromiseProxyMixin);

export default Ember.Component.extend({
  proposal:        null,
  participant:     null,
  // previousSupport: [],

  actions: {
    toggleSupport: function(proposal, participant){
      this.set('proposal', proposal);
      this.set('participant', participant);

      var previousSupportQuery = {
        query: {
          filter: {
            proposal_id: this.get('proposal.id'),
            participant_id: this.get('participant.id')
          }
        }
      };

      var self = this
      this.container.lookup('service:supports').find(previousSupportQuery).then(function(resources) {
        if( Ember.isEmpty(resources) ) {
          self.addSupport();
        } else {
          self.removeSupport(resources);
        }
      });
    }
  },

  addSupport: function() {
    var support = this.container.lookupFactory('model:supports').create();
    support.addRelationship('proposal', this.get('proposal.id'));
    support.addRelationship('participant', this.get('participant.id'));

    this.store.createResource('support', support);
  },

  removeSupport: function(resources) {
    this.store.deleteResource('support', resources.get('firstObject'));
  }

  // alreadySupported: Ember.computed('proposal.id', function() {
  //   return !Ember.isEmpty(this.get('previousSupport'));
  // }),
  //
  // previousSupport: Ember.computed('proposal.id', 'participant.id', function() {
  //   var query = {
  //     query: {
  //       filter: {
  //         proposal_id: this.get('proposal.id'),
  //         participant_id: this.get('participant.id')
  //       }
  //     }
  //   };
  //
  //   return PromiseObject.create({
  //     promise: this.container.lookup('service:supports').find(query)
  //   });
  // })
});

as mentioned in slack return !Ember.isEmpty(this.previousSupport); needs to use this.get like so return !Ember.isEmpty(this.get('previousSupport'));

@pixelhandler just went with a callback after the find() for now, not that bad in the end