Soundcloud Javascript API SC.get（）不允许我更改函数之外的变量 [英] Soundcloud Javascript API SC.get() will not allow me to change a variable outside of the function

问题描述

我似乎在Soundcloud Javascript API中遇到了SC.get函数的问题。我尝试将一个新项目推送到newSounds数组;但是，在_.each循环退出后，newSounds对象仍然是一个长度为0的数组。此外，在loadSounds执行后声音对象未定义。一些帮助将不胜感激，如果我需要发布更多帮助解决问题，请告诉我。

I seem to be having a issue with the SC.get function in the Soundcloud Javascript API. I try to push a new item to the newSounds array; however, after the _.each loop exits the newSounds object is still an array with length = 0. In addition the sounds object is undefined after loadSounds executes. Some help would be greatly appreciated, and if I need to post more to help solve the problem let me know.

loadSounds = function() {
    var newSounds = [];
    _.each(trackURLs, function(trackURL) {
      console.log(trackURL);
      SC.get(trackURL, function(track) {
        console.log(track.artwork_url);
        newSounds.push(track);
      });
    });
    return newSounds;
};

var sounds = loadSounds();

推荐答案

在这种情况下，棘手的是 SC.get 很可能是异步的，所以当你返回 newSounds 时，它几乎肯定是空的/不完整的。最重要的是，有多个要管理的 SC.get 的调用。

The tricky thing in this case is that SC.get is most likely asynchronous, so when you go to return newSounds it will almost certainly be empty/incomplete. On top of that, there are multiple calls to SC.get to manage.

使用<$ c $在jQuery中c> deferred 对象，你可以解决你的问题像这样的问题（灵感来自 http://www.tentonaxe.com/index.cfm/2011/9/22/Using-jQuerywhen-with-a-dynamic-number-of-objects ）：

Using the deferred object in jQuery, you could solve your problem like this (inspired by http://www.tentonaxe.com/index.cfm/2011/9/22/Using-jQuerywhen-with-a-dynamic-number-of-objects):

function loadSounds() {
    var newSounds = [];

    var deferredObjects = $.map(trackURLs, function (item, index) {
        var deferred = $.Deferred();

        SC.get(trackURL, function(track) {                 
            newSounds.push(track);
            deferred.resolve(track);
        });

        return deferred.promise();
    });

    $.when.apply(this, deferredObjects).then(function () {
        console.log('All done');
        console.log(newSounds);
    });

    return newSounds;
}

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