Angularjs $ q.all [英] Angularjs $q.all

问题描述

我已经实现在angularjs的$ q.all，但我不能让code工作。这里是我的code：

I have implemented the $q.all in angularjs, but I can not make the code working. Here is my code :

UploadService.uploadQuestion = function(questions){

        var promises = [];

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

            var deffered  = $q.defer();
            var question  = questions[i]; 

            $http({

                url   : 'upload/question',
                method: 'POST',
                data  : question
            }).
            success(function(data){
                deffered.resolve(data);
            }).
            error(function(error){
                deffered.reject();
            });

            promises.push(deffered.promise);
        }

        return $q.all(promises);
    }

这是我的控制器调用其中的服务：

And here is my controller which call the services:

uploadService.uploadQuestion(questions).then(function(datas){

   //the datas can not be retrieved although the server has responded    
}, 
function(errors){ 
   //errors can not be retrieved also

})

我认为有一些问题，我的服务设置$ q.all。任何帮助真的AP preciated。谢谢你。

I think there is some problem setting up $q.all in my service. Any help really appreciated. Thank you.

推荐答案

在JavaScript的没有 块级范围 仅 函数级别范围

In javascript there are no block-level scopes only function-level scopes:

阅读这篇文章，了解 javaScript的范围和提升。

var deferred = $q.defer();
deferred.count = i;

console.log(deferred.count); // 0,1,2,3,4,5 --< all deferred objects

// some code

.success(function(data){
   console.log(deferred.count); // 5,5,5,5,5,5 --< only the last deferred object
   deferred.resolve(data);
})

• 当你写 VAR推迟= $ q.defer（）; 里面的for循环它的悬挂的函数的顶部，它也就是说JavaScript的声明循环。
之外的功能范围，这个变量

• 每次循环，最后的延迟的被覆盖previous之一，没有块级范围，保存到对象的引用。


• 当异步回调（成功/错误）被调用，他们只引用最后的延期对象并只有它得到解决，所以 $ q.all从未解决，因为它仍在等待其他递延对象。


• 您需要的是为你遍历每个项目创建一个匿名函数。


• 由于功能确实有范围，则参考递延对象是在 关闭范围preserved 函数执行后还是一样。


• 作为#dfsq评论：无需手动构建一个新的Deferred对象，因为$ HTTP本身返回的承诺。
  

  ---



• When you write var deferred= $q.defer(); inside a for loop it's hoisted to the top of the function, it means that javascript declares this variable on the function scope outside of the for loop.
• With each loop, the last deferred is overriding the previous one, there is no block-level scope to save a reference to that object.
• When asynchronous callbacks (success / error) are invoked, they reference only the last deferred object and only it gets resolved, so $q.all is never resolved because it still waits for other deferred objects.
• What you need is to create an anonymous function for each item you iterate.
• Since functions do have scopes, the reference to the deferred objects are preserved in a closure scope even after functions are executed.
• As #dfsq commented: There is no need to manually construct a new deferred object since $http itself returns a promise.

  ---

下面是一个演示plunker：<一href=\"http://plnkr.co/edit/NGMp4ycmaCqVOmgohN53?p=$p$pview\">http://plnkr.co/edit/NGMp4ycmaCqVOmgohN53?p=$p$pview

Here is a demo plunker: http://plnkr.co/edit/NGMp4ycmaCqVOmgohN53?p=preview

UploadService.uploadQuestion = function(questions){

    var promises = [];

    angular.forEach(questions , function(question) {

        var promise = $http({
            url   : 'upload/question',
            method: 'POST',
            data  : question
        });

        promises.push(promise);

    });

    return $q.all(promises);
}

我最喜欢的方式是使用阵列＃地图：

下面是一个演示plunker：<一href=\"http://plnkr.co/edit/KYeTWUyxJR4mlU77svw9?p=$p$pview\">http://plnkr.co/edit/KYeTWUyxJR4mlU77svw9?p=$p$pview

UploadService.uploadQuestion = function(questions){

    var promises = questions.map(function(question) {

        return $http({
            url   : 'upload/question',
            method: 'POST',
            data  : question
        });

    });

    return $q.all(promises);
}

这篇关于Angularjs $ q.all的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！