Backbone.js this.collection.models在渲染视图时有效，但在其他地方调用时返回空数组

Question

var Order = Backbone.Model.extend({
    url: function() {
        return 'http://localhost:51782/api/orders/'+this.id;
    }
}); 

var DataSetOrders = Backbone.Collection.extend({
        url: "http://localhost:51782/api/orders",
        model: Order,

    initialize: function(){
        this.fetch({
            success: this.fetchSuccess,
            error: this.fetchError
        });
    },

    // This is where my data is being extracted I am returning the 
    // response since its an array of all the objects within my database
    // perhaps i should not use return? Is there a way to save this information so it can always
    // be available when i call DataSetOrders();?

    fetchSuccess: function (collection, response) {
        // console.log('Collection fetch success', response);
        // console.log('Collection models: ', collection.models);
        return response;
    },

    fetchError: function (collection, response) {
        throw new Error("Orders fetch error");
    }
});

var DataSetOrdersView = Backbone.View.extend({
        el: $("#orders"),
    // collection: new DataSetOrders(),

    initialize: function () {
        this.collection = new DataSetOrders();

        this._modelBinder = new Backbone.ModelBinder();

        this.render();
        this.$el.find("#filter").append(this.createSelect()); 

        this.on("change:filterType", this.filterByStatus, this);
        this.collection.on("reset", this.render, this);

        this.collection.on("add", this.renderOrder, this);
        this.collection.on("remove", this.removeOrder, this);
    },

    render: function () {
        this.$el.find("article").remove();

        // This is the line where we are getting all of our models and rendering it to the #orders view
        // as you can see it is referencing the this.collection = new DataSetOrders()
        // This is actually working the view is being rendered and I can see the orders being pulled from 
        // the database 
        _.each(this.collection.models, function (item) {
            this.renderOrder(item);
        }, this);
    },

    renderOrder: function (item) {

        // The item which is an element of the previous array returned is now being placed in the model
        // and its being rendered prefectly.
        var orderView = new OrderView({
            model: item
        });
        this.$el.append(orderView.render().el);
        // this.$el.append(this._modelBinder.bind(orderView.render().el));
    },

    getTypes: function () {
        // HERE!!! IS where this.collection is now = [] wtf?!? I dont know why its doing this pleace help me!!
        return _.uniq(this.collection.pluck("OrderStatus"), false, function (type) {
            return type.toLowerCase();
        });
    },

抱歉长码，但我有一个简单的问题。为什么我的代码在使用方法时第一次调用render.collection具有其中的元素，并且由于我的代码结构，它呈现我的数据库对象并且完美地工作。但是当我在geTypes函数上再次调用this.collection时，我得到一个空数组，我不明白它是怎么回事？