如何在Ember.js中的多态关系上声明`type`键？

Question

我正在尝试学习ember.js，我在尝试将DS.FixtureAdapter与模拟数据一起使用时遇到了问题。每当我尝试访问商店时，我都会收到Ember错误：

处理路径时出错：练习断言失败：Ember数据需要一个数字或字符串来表示pictureExercises关系中的记录，而不是找到一个对象。如果这是多态关系，请指定type密钥。如果这是嵌入式关系，请添加DS.EmbeddedRecordsMixin*并在序列化程序的attrs哈希中指定pictureExercises属性。

查看ember检查器中的余烬数据部分，我可以看到所有顶级练习数据都已正确加载，而PictureExercises和VideoExercises则没有。

如何在Ember.js中声明多态关系的type键？

我完全失去了任何帮助，我们将不胜感激。 感谢您的时间。

//Create application store    
Gymbo.ApplicationAdapter = DS.FixtureAdapter;

//Set up models and relationships
    Gymbo.Exercise = DS.Model.extend({
        //id: DS.attr("number"), /*Ember will error if id is in model* /
        name: DS.attr("string"),
        description: DS.attr("string"),        
        pictureExercises: DS.hasMany("pictureExercise", {async: true }),
        videoExercises: DS.hasMany("videoExercise", { async: true }) 
    });


Gymbo.PictureExercise = DS.Model.extend({
        //id: DS.attr("number"),
        exerciseId: DS.attr("number"),       
        mimeType: DS.attr("string"),
        picFilePath: DS.attr("string"),
        picName: DS.attr("string"),
        exercise: DS.belongsTo("exercise")
    });

    Gymbo.VideoExercise = DS.Model.extend({
        //id: DS.attr("number"),
        exerciseId: DS.attr("number"),       
        videoName: DS.attr("string"),
        videoFilePath: DS.attr("string"),
        videoType: DS.attr("string"),
        exercise: DS.belongsTo("exercise")
    });

//UsersRoute
    Gymbo.ExercisesRoute = Ember.Route.extend({
        model: function () {
            return this.store.find("exercise");                      
        }
    });

//MOCK DATA
    Gymbo.Exercise.reopenClass({
        FIXTURES:
          [
            {
                "id": 101,
                "name": "Exercise 1",
                "description": "Description here",
                "pictureExercises": [
                    {
                        "id": 106,
                        "exerciseId": 101,                        
                        "mimeType": "PNG",
                        "picFilePath": "images\\strength",
                        "picName": "s001"                        
                    },
                    {
                        "id": 107,
                        "exerciseId": 101,                       
                        "mimeType": "JPG",
                        "picFilePath": "images\\strength",
                        "picName": s002
                    }
                ],
                "videoExercises": [
                    {
                        "id": 101,
                        "exerciseId": 101,                       
                        "videoName": "Test",
                        "videoFilePath": "Video\\strength",
                        "videoType": "mp4"
                    }
                ]
            },
            {
        "id": 102,
                //Data removed for brevity.....
            }
          ]
    });