我想从jQuery getJSON调用中另一个对象获取的数据实例化新对象。我发现了承诺对象,并且我认为我可以用它来实现这一点。下面是我实现的:getJSON完成后实例化对象
function HeadlineList(url) {
this.url = url;
this.checkEmpty = function() {
if (this.quantity === 0) {
this.refreshContent();
}
};
this.getRandom = function(remove) {
var headlineNumber = Math.floor(Math.random()*this.quantity);
var headlinePick = this.list[headlineNumber];
if (remove) {
this.deleteHeadline(headlineNumber);
}
return headline;
};
this.getHeadline = function(number, remove) {
var headlinePick = this.list[number]
if (remove) {
this.deleteHeadline(number);
}
return headline;
};
this.deleteHeadline = function(number) {
this.list.splice(number, 1);
this.quantity -= 1;
};
this.fillFromJSON = function(data) {
this.list = data.headlines;
this.quantity = this.list.length;
};
// Here's where I create the promise object. 'response' is globally
// scoped so my other objects can get to it.
this.refreshContent = function() {
response = $.when($.getJSON(this.url, this.fillFromJSON));
};
this.refreshContent();
}
当HeadlineList
对象被实例化,它使用的getJSON获取数据。这个AJAX请求存储在response
全局变量中,所以我可以确保它在稍后完成。在此之后,我想要创建一个不同的对象,但数据取决于正确实例化的这个HeadlineList
。我尝试使用response
的done
方法来完成此操作。
有问题的类:
function Headline(object) {
this.title = object.title;
this.url = object.url;
this.onion = object.onion;
this.isOnion = function(){
return this.onion;
}
}
和类的实例化一个HeadlineList
对象后的实例:
// headlines is an instance of HeadlineList with the URL of my JSON file.
// It should (and does) make the request when instantiated.
headlines = new HeadlineList('js/headlines.json');
// Instantiating the headline after the AJAX request is done. Passing
// a random headline from the HeadlineList object to the constructor.
response.done(function() {
headline = new Headline(headlines.getRandom(true));
});
我已经看过了Chrome的DevTools网络选项卡,以确保没有什么JSON文件错误。它给出了一个200响应,并在JSON linter中进行验证。 headlines
对象的list
属性应包含来自该文件的数据,但它始终未定义。
var headlinePick = this.list[headlineNumber];
唯一的例外是Uncaught TypeError: Cannot read property 'NaN' of undefined
:该项目在此线路上headlines
对象的getRandom
方法里面打一个例外。
我不确定问题的确切位置或从哪里去。任何指导将不胜感激。
或者更简单地说'响应= $。当($的getJSON(this.url,this.fillFromJSON.bind(本)));' – bmceldowney 2013-05-08 22:36:20
这是问题。谢谢你们俩! – raddevon 2013-05-08 23:53:20