问题描述
我之前曾在 jQuery 中使用过 Promise - 但我无法将它应用于这种情况.我更喜欢使用 $.when() 和 $.done() 方法来实现这一点.
I have used promises in jQuery slightly before - but I am having trouble applying it to this scenario. I prefer to use the $.when() and $.done() methods to achieve this.
据我所知，我需要构建一个 $.Deferred 对象来记录请求，当这些请求完成时 - 触发回调.在我下面的代码中，回调在 ajax 请求之前触发 而不是之后 - 也许我只需要一些睡眠
From what I understand I need to build a $.Deferred object which logs the requests and when those requests are finished - fire the callback. In my code below the callback is firing before the ajax requests and not after - maybe I just need some sleep
我知道我的代码不完整，我一直在努力通过添加 for 循环来应用它.
I know my code is incomplete I have been struggling to apply it with the addition of the for loop.
http://jsfiddle.net/whiteb0x/MBZEu/
var list = ['obj1', 'obj2', 'obj3', 'obj4', 'obj5'];
var callback = function() {
alert("done");
};
var requests = [];
var ajaxFunction = function(obj, successCallback, errorCallback) {
for(i = 0; i < list.length; i++) {
$.ajax({
url: 'url',
success: function() {
requests.push(this);
}
});
}
};
$.when($.ajax(), ajaxFunction).then(function(results){callback()});
推荐答案
$.when 的参数应该是 $.ajax 的返回值，它也不会不需要单独调用——这是没有意义的.你想要这样的东西:
The arguments to $.when should be the return value of $.ajax, which also doesn't need to be called separately -- that makes no sense. You want something like this:
for (i = 0; i < list.length; i++) {
requests.push($.ajax(...));
}
$.when.apply(undefined, requests).then(...)
需要 .apply 的原因是因为 $.when 可以接受多个参数，但不能接受参数数组..apply 本质上扩展为:
The reason that .apply is needed is because $.when can take multiple arguments, but not an array of arguments. .apply expands essentially to:
$.when(requests[0], requests[1], ...)
这也假设请求可以按任何顺序完成.
This also assumes that the requests can be completed in any order.
http://jsfiddle.net/MBZEu/4/ -- 注意 'done' 记录到控制台在所有成功消息之后.
http://jsfiddle.net/MBZEu/4/ -- notice that 'done' is logged to the console after all of the success messages.
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