异步Javascript函数，不返回值 [英] Async Javascript functions, not returning values

问题描述

我遇到一个困扰我的问题.基本上是这样的情况:

I'm having an issue that is burning my head. Basically this is the scenario:

我有一个 callController()函数，只需使用 jQuery.load()方法来加载控制器，加载后，我就可以玩返回参数.

I have a callController() function, which just simple use the jQuery.load() method to load a controller, after loaded, I can play with the returning parameters.

现在...在我的一个控制器中，我需要检查一个验证规则，以允许用户执行某些功能，但是，我创建了一个像这样的功能:

Now... in one of my controllers there is a validation rule I need to check in order to to allow the user to execute certain functionality, however, I create a function like this:

function myValRule() {

    var val = callController('blablabla'),
    response = "";
    val.done(function(data) {
        //my business logic
        response = something;
    }
    return response;

}

如您所料， response ，即使它有一个值，它也会返回 undefined ，因此我设置了超时时间和 console.log()它现在有一个值，但是即使将返回值放入 setTimeout()中，我也无法返回该值.因此，基本上，当该方法调用此函数进行验证时，它会发现它为空.

As you imagine, response, even if It has a value, it returns undefined, so I set a timeout and console.log() it and now it has a value, but I cannot make to return this value even if I put the return into the setTimeout(). So basically when the method call this function to validate it finds it empty.

您能指出我解决这个问题的方向吗?

Can you point me on some direction to solve this issue?

推荐答案

请记住，这是异步的！ return response; 早在实际调用 .done()的时候就消失了.

Remember this is asynchronous! The return response; is long gone by the time .done() is actually called.

如果您需要以这种方式返回的值，请查看在您的 myValRule 函数中提供了一个回调函数(将从 .done()内部调用)或是看看使用 $.Deferred api，这样您就可以模仿 callController(...)在做什么.

if you need the value returned in this fashion, look at either supplying a callback function in your myValRule function (that would be called from within .done()) or maybe look at using the $.Deferred api so you can mimic what callController(...) is doing.

这是这两种情况的示例(带有对 myValRule 的示例调用):

Here's an example of both scenarios (with example call to myValRule):

function myValRule(callback){
  var val = callController('blablabla'),
  val.done(function(data){
    var response = /* something */;
    callback(response);
  });
}
myValRule(function(response){
  // here you have response
});

使用$ .Deferred

(我想是jQuery，因为有一个.done调用)

Using $.Deferred

(I assume it's jQuery since there's a .done call)

function myValRule(){
  var df = $.Deferred(),
      val = callController('blablabla');
  val.done(function(data){
    var response = /*something */;
    df.resolve(response);
  }).fail(df.reject);
  return df.promise();
}
myValRule().done(function(response){
  // here you have response
});

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