Ember Query or Create Pattern

route.js

import Ember from 'ember';

export default Ember.Route.extend({
  currentModel: null,
  singleModel: false,
  
  model: function(){
    function closure(username) {
      // using firebase adapter
      return store.query('user', {
        orderBy: 'username',
        equalTo: username
      }).then(function(array){
        if(array.get('length') === 0){
          var usr = store.createRecord('user', {
            username: username
          });
          self.set('singleModel', true);
          return usr.save();
        }
        return array;
      });
    }
    var self = this;
    var store = this.store;
    // getData() omitted for brevity 
    return this.getData().then(function(value){
      return closure(value);
    });
  },
  /*
   * the model returned from the model hook can be an array or a single model
   * here we determine which and set the controller model appropriately 
   */
  renderTemplate: function(controller, model){
    if(this.get('singleModel')){
      this.set('currentModel', model);
      this.render('controlPanel', {});
    }else {
      // in my case I always expect a single model
      this.set('currentModel', model.get('firstObject'));
      controller.set('model', this.get('currentModel'));
      this.render('controlPanel', {});
    }
  }
});