重写Backbone.js比较器

Question

我有一个简单的backbone.js twitter应用程序,需要以相反的顺序排序推文.我目前按日期实施了一个比较器排序.单击"反向"按钮时(如视图中所示)如何反转排序所有推文而不返回比较器？我的印象是,当我调用sort时,它将尝试重新呈现列表(这意味着比较器将再次对数据进行排序,这是不合需要的).我该如何覆盖它？

Tweet = Backbone.Model.extend();

 // Define the collection
Tweets = Backbone.Collection.extend(
{
    model: Tweet,
    // Url to request when fetch() is called
    url: 'http://search.twitter.com/search.json?q=codinghorror',

    parse: function(response) {

        //modify dates to be more readable
        $.each(response.results, function(i,val) {
            val.created_at = val.created_at.slice(0, val.created_at.length - 6);
          });

        return response.results;
    },
    // Overwrite the sync method to pass over the Same Origin Policy
    sync: function(method, model, options) {
        var that = this;
            var params = _.extend({
                type: 'GET',
                dataType: 'jsonp',
                url: that.url,
                processData: true
            }, options);

        return $.ajax(params);
    },
    comparator: function(activity){

        var date = new Date(activity.get('created_at'));
        return -date.getTime();

    }
});

   // Define the View
  TweetsView = Backbone.View.extend({
initialize: function() {
  _.bindAll(this, 'render');
  // create a collection
  this.collection = new Tweets;
  // Fetch the collection and call render() method
  var that = this;
  this.collection.fetch({
    success: function (s) {
        console.log("fetched", s);
        that.render();
    }
  });
},

el: $('#tweetContainer'),
// Use an external template

template: _.template($('#tweettemplate').html()),

render: function() {
    // Fill the html with the template and the collection
    $(this.el).html(this.template({ tweets: this.collection.toJSON() }));
},

events : {
    'click .refresh' : 'refresh',
    **'click .reverse' : 'reverse'**
},

refresh : function() {

 this.collection.fetch();
console.log('refresh', this.collection);
 this.render();

},

**reverse : function() {**

    console.log("you clicked reverse");

    console.log(this.collection, "collection");

    this.collection.sort();

   //How do I reverse the list without going through the comparator?

**}**

});

var app = new TweetsView();
 });

Answer 1

Backbone问题的常见解决方案是使用事件.通话sort将触发"reset"事件:

调用sort会触发集合的"reset"事件,除非通过传递进行静音{silent: true}.

所以你可以在你的集合中有一个"排序顺序"标志:

Backbone.Collection.extend({
    //...
    initialize: function() {
        //...
        this.sort_order = 'desc';
        //...
    }
});

然后你comparator可以注意那个标志:

comparator: function(activity) {
    var date = new Date(activity.get('created_at'));
    return this.sort_order == 'desc'
         ? -date.getTime()
         :  date.getTime()
}

你可以在集合上有一个方法来改变排序顺序:

reverse: function() {
    this.sort_order = this.sort_order = 'desc' ? 'asc' : 'desc';
    this.sort();
}

然后,您的视图可以侦听"reset"事件,并在更改排序顺序时重新显示集合.一旦完成所有这些,您只需告诉您的反向按钮即可拨打电话view.collection.reverse(),一切都会好起来的.

演示:http://jsfiddle.net/ambiguous/SJDKy/