骨干设置模型的条件

Question

我在骨干中有一个应用程序，有一些按钮，我可以添加动态可拖动和可调整大小的元素。这个元素被添加到模型的集合中，当我停止例如拖动我设置我的元素的新坐标，但是alays设置最后元素不是我拖动的元素。我怎么解决？ 这是我的应用视图

define(['jquery' , 
        'backbone', 
        'jquery_ui',
        'models/design', 
        'collections/design', 
        'views/element',
        "text!templates/design.html"
        ], 
    function($, Backbone, jQueryUI, DesignModel, DesignCollection, ElementView, tmplDesign){
    var DesignView = Backbone.View.extend({
        initialize: function(){
            this.$el = $('#layout');
            this.template = tmplDesign;
            this.elementModel = null;
            this.collection = new DesignCollection();
            var here = this;
            $('#insert-dynamic-element').click(function(){
                var element = { designId:here.collection.models.length  , name:'img', type:'image', width:'100px', height:'50px', top:'0', left:'0'};
                here.elementModel = new DesignModel(element);
                here.collection.addElement(here.elementModel);
                here.render();
                $(function() {
                    $('.drag-item').draggable({
                        snap        : true,
                        cursor      : "move",
                        delay       : 100,
                        scroll      : false,
                        containment : "parent",
                        stop: function (e, ui){
                            here.elementModel.set({ left:$(this).css('left'), top: $(this).css('top')});
                            here.collection.set(here.elementModel, {remove:false});
//--------------- HERE I WANT TO SET THE RIGHT ELEMENT DRAGGED NOT THE LAST!!! ------------------------------
                        }
                    });
                });
            });
        },
        render: function(){
            var template = _.template(this.template, {elements:this.collection.toJSON()});
            this.$el.empty();
            this.$el.html(template);
        }
    })

    return DesignView;
});