Question

我有一个错误，计算属性会暂时变为不正确的值。

JSBin复制错误：http://jsbin.com/yufet/6/edit?js,console

// ember.js 1.6.0-beta.1+canary.8d91bf06
// ember-data 1.0.0-beta.7+canary.02d7c7be

App.Playlist = DS.Model.extend({
  tracks: DS.hasMany('track', { inverse: 'playlist' }),
  sortProperties: ['trackOrder:asc'],
  sortedTracks: Ember.computed.sort('tracks', 'sortProperties'),
  queuedTracks: Ember.computed.filterBy('sortedTracks', 'isQueued'),
  currentTrack: Ember.computed.alias('queuedTracks.firstObject')
});

App.Track = DS.Model.extend({
  playlist: DS.belongsTo('playlist', { inverse: 'tracks' }),
  title: DS.attr('string'),
  trackOrder: DS.attr('number'),
  isOrdered: Ember.computed.notEmpty('trackOrder'),
  playedAt: DS.attr('date'),
  hasPlayed: Ember.computed.notEmpty('playedAt'),
  hasNotPlayed: Ember.computed.not('hasPlayed'),
  isQueued: Ember.computed.and('isOrdered', 'hasNotPlayed')
});

然后是我的主要人物：

store = App.__container__.lookup('store:main');

store.pushPayload('playlist', {
  "playlist": {
    "id":1,
    "title":"Playlist 1",
    "track_ids":[1,2,3,4,5]
  },"tracks":[
    { "id":1, "playlist_id":1, "title": "Track 0", "track_order": 5, "played_at":null },
    { "id":2, "playlist_id":1, "title": "Track 1", "track_order": 10, "played_at":null },
    { "id":3, "playlist_id":1, "title": "Track 2", "track_order": 15, "played_at":null },
    { "id":4, "playlist_id":1, "title": "Track 3", "track_order": 20, "played_at":null },
    { "id":5, "playlist_id":1, "title": "Track 4", "track_order": 25, "played_at":null }
  ]
});

store.find('playlist', 1).then(function(pl) {
  playlist = pl;
  var observer = Ember.Object.create({
    logMessage: function(room) {
      console.log('currentTrack changed to', playlist.get('currentTrack.title'));
    }
  });

  playlist.addObserver('currentTrack', observer, 'logMessage');
  playlist.get('currentTrack.title');
  track = playlist.get('tracks').createRecord({ title: 'A new song!!'});
  track.set('trackOrder', 30);
});

输出：

currentTrack changed to A new song!!
currentTrack changed to Track 0

track.trackOrder仅限null或30。当它为null时，我希望isQueued为false并过滤掉该曲目。当它是30时，它应该在列表的最后。

如果我没有在观察者本身中拨打get('currentTrack.title')，currentTrack仍为A new song!!。

Answer 1

在Stefan Penner的黑客时刻获得一些帮助后想出来。

您无法在模型上使用sortProperties，因为它是Ember.SortableMixin提供的，只会与控制器混合使用。

我认为它实际上并没有排序。哈！

为什么这个Ember.computed属性的观察者会发射两次？

1 个答案: