问Backbone javascript视图不重新渲染

EN

(function(){
window.App = {
    Models: {},
    Collections:{},
    Views: {}
};

window.template = function(id) {
    return _.template($('#'+id).html());
};

App.Models.Task = Backbone.Model.extend({
    validate: function(attrs){
        if (! attrs.title){
            return 'A task requires a valid title';
        }
    }
});

App.Collections.Task = Backbone.Collection.extend({
    model: App.Models.Task
});

App.Views.Tasks = Backbone.View.extend({
    tagName: 'ul',

    render: function(){
        this.collection.each(this.addOne,this);
        return this;
    },

    addOne: function(task){
    var taskView = new App.Views.Task({model:task});
    this.$el.append(taskView.render().el);

    }

});

App.Views.Task = Backbone.View.extend({

    tagName: 'li',

    template: template('taskTemplate'),

    initalize: function(){
        this.model.on('change:title',this.render,this);  
        this.model.on('destory',this.remove,this);
    },

    events: {
       'click .edit': 'editTask',
        'click .delete': 'destroy'
    },

    editTask: function(){
    var newTaskTitle =  prompt('what is the new text for the task ?',this.model.get('title')); 

        if(!newTaskTitle)return;

        this.model.set('title',newTaskTitle);
    },

    destroy: function(){
        this.model.destroy();            
    },

    remove:function(){
    this.$el.remove();
    },

    render: function(){
        var template = this.template(this.model.toJSON());
        this.$el.html(template);
        return this;
    }
});

window.taskCollection = new App.Collections.Task([
    {
        title: 'Go to the store',
        priority:3
    },
    {
        title: 'Go to gym',
        priority:2
    },
    {
        title: 'Learn backbone',
        priority:1
    }
]);

var taskView = new App.Views.Tasks({collection:taskCollection});
$('.tasks').html(taskView.render().el);
})();