$ .getJSON在for循环中调用行为不端

问题描述

以下是对我的问题的描述：

Here's a description of my problem:

我有一个包含某些flickr照片的ID的数组。
为每个id，我需要制作两个嵌套的apiCalls（一个用于flickr photosets api，一个用于photoinfo api）并在我的页面中添加一些html

i have an array containing ids for some flickr photosets.for each id, i need to make two nested apiCalls (one to flickr photosets api, one to photoinfo api) and add some html to my page

结构是：

for(var i=0; i<ARRAY_ID.length; i++){

    $.getJSON(apiCall, function(data) {
         // some processing here

         $.getJSON(apiCall2,function(data){
              //other processing here

每个apiCall是一个字符串，包含对photosets api（apiCall）的正确调用，然后是在所有这些处理之后，在apiCall2块中，我将一些html附加到一个div（这导致与ARRAY_ID一样多的块元素）photoInfo api（apiCall2）

each "apiCall" is a string containing the correct call to the photosets api (apiCall) and then for the photoInfo api (apiCall2)

长度）。

我有奇怪的行为：所有附加的块元素包含相同的文本，图片和链接。它以预期的数字打印出来，但是内容与所有内容相同。我想是的for循环不等待$ .getJSON完成。我怎样才能实现这一目标？我严格要求在处理下一个json请求之前完成每个json请求！谢谢大家！

There's where i have the strange behaviour: all appended block elems contain the same text and picture and links. It prints them out in the expected number, but the content is the same throu all of them. I guess it's the for loop not waiting for the $.getJSON to finish. How can i achieve this? I strictly need each json request to be finished before the next one is processed! Thanks all!

推荐答案

您似乎有2个不同但相关的问题。

You seem to have 2 different, but related, issues going here.

如果你引用<$回调中的c $ c> i ，您需要将其包含在中。否则，当 $。getJSON 异步时，的将在调用回调之前完成，并且 i 将始终是循环中的最后一个值 - ARRAY_ID.length ：

If you're referencing i within the callbacks, you'll need to enclose it within the for. Otherwise, with $.getJSON being asynchronous, the for will finish before the callbacks are called and i will always be the last value in the loop -- ARRAY_ID.length:

for(var i = 0; i < ARRAY_ID.length; i++) {
    (function (i) {
        // work with the local `i` rather than the shared `i` from the loop
    })(i);
}

---

---

你不能得到 for 等待每组 $。getJSON 完成。但是，您可以使用 for 循环和闭包来构建，等待您明确告诉 next 继续：

You can't get the for to "wait" for each set of $.getJSON to finish. You can, however, use the for loop and closures to build a queue, which waits until you explicitly tell it next to continue:

var focus = $(...); // either match an existing element or create one: '<div />'

for(var i = 0; i < ARRAY_ID.length; i++) {
    (function (i) {
        focus.queue('apicalls', function (next) {
            $.getJSON(apiCall, function(data) {
                 // some processing here

                 $.getJSON(apiCall2,function(data){
                      //other processing here

                      next(); // start the next set of api calls
                 });
            });
        });
    })(i);
}

focus.dequeue('apicalls');

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