AngularJS的Firebug中关于ng选项的奇怪错误

当我使用Angular的ng选项时，我得到了一个奇怪的错误：

Error: [ngOptions:iexp] Expected expression in form of '_select_ (as _label_)? for (_key_,)?_value_ in _collection_' but got 'playlist.id as playlist.name in playlists | orderBy: 'playlist''. Element: <select class="ng-pristine ng-valid" name="playlist" ng-model="playlist" ng-options="playlist.id as playlist.name in playlists | orderBy: 'playlist'">

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正确的语法是播放列表中播放列表的

playlist.id as playlist.name…

<select name="playlist" ng-model="playlist" ng-options="playlist.id as playlist.name in playlists | orderBy: 'playlist'"></select>
<button class="btn btn-branded" ng-click="postSongToPlaylist(playlist.id);">Save</button>

    MediaService.getPlaylists().then(function (response) {
        $scope.playlists = response.data.data;
    });

    $scope.postSongToPlaylist = function(playlist_id) {
        media = {
            id: $rootScope.song_id
        };
        MediaService.postSongToPlaylist(playlist_id, media).then(function (response) {});
    }