如何在 angularjs 的循环中调用第二个顺序承诺设计模式方法? [英] How can I call the second sequential promise design pattern method in a loop in angularjs?

问题描述

刚接触 angularjs 并第一次尝试 promise 模式 -

New to angularjs and trying out the promise pattern for the first time -

我有一个服务实用程序，里面有这个方法 -

I have a service utility inside which I have this method -

this.getData= function(url){
        var defer = $q.defer();

        $http({method: 'GET', url: url}).
            success(function(data, status){
                defer.resolve(data);
            })
            .error(function(data, status) {
                defer.reject(status);
            });

        return defer.promise;
    };

现在在我的控制器中，我正在调用一个名为 A() 的方法

Now inside my controller, I am calling a method called A()

   var A = function () {
    $scope.myobjectArray = [];


    return utility.getData("some url").then(funciton(data)
    {

        for (i = 0; i < data.length; i++) {
            $scope.myobjectArray.push(data[i].attribute1, new Array());

        }

    }
    ).
    then(function () {

        return getTheSecondAttributeArray();
    }).catch(function (status) {
//display error

    });


};

var getTheSecondAttributeArray = function () {

    for (i = 0; i < $scope.myObjectArray.length; i++) {
        var secondAttributeArray = [];
        var currentType = $scope.myObjectArray[i];
        utility.getData("some url").then(function (response) {
            for (j = 0; j < response.length; j++) {
//some response manipulation
                secondAttributeArray.push(response[j].text);
            }
        currentType.secondAttribute = secondAttributeArray;
        }).catch(function () {//catch error, display message
        })

    }
}

但是，看起来 $scope.myobjectArray 的最后一个元素(第 n-1 个元素)只会被填充.此外，最后一个元素包含的 secondAttributeArray 是 $scope.myobjectArray 的所有对象的所有 secondAttributes 的串联数组.

However, it looks like that the last element of the $scope.myobjectArray (n-1th element) is only getting populated. Also, the secondAttributeArray that this last element contains is a concatenated array of all secondAttributes for all objects of the $scope.myobjectArray.

不知道我可以在这里更改什么.

Cannot figure out what can I change here.

当我尝试在then"函数中访问 $scope.myObjectArray[j] 时，它说 $scope.myObjectArray[j] 未定义.--> 所以我创建了一个 currentType 变量并将 $scope.myObjectArray[j] 分配给它，这在then"函数中很容易访问.奇怪！

When I tried accessing $scope.myObjectArray[j] inside the 'then' function, it said $scope.myObjectArray[j] was undefined. --> And so I created a currentType variable and assigned $scope.myObjectArray[j] to it and that was easily accessible inside the 'then' function. Weird!

另外，我看到只有 $scope.myObjectArray 的最后一个对象获取值，其余的没有.数组中的其余对象为空

Also, I see that only the last object of the $scope.myObjectArray gets values and not the rest. The rest of the objects in the array are empty

感谢任何帮助.

var myObject = function(firstattribute, secondAttribute){

this.firstattribute = firstattribute;
this.secondAttribute = secondAttribute;
}

Beehive 的解释 (Angularjs $q.all) 是我面临的问题.我只得到最后一个循环的数据.

The explanation here by Beehive (Angularjs $q.all) is something that I am facing. I only get the last loop's data.

推荐答案

问题全在于函数闭包.当获取数据返回时，您的 currentType 是最后一个，因为 for j 循环已经结束.所以你需要做的是将代码从 utility.getData 移动到一个单独的方法，传递 currentType 和 seccondAttributeArray 的参数，所以闭包将包含它们作为函数的参数，并且不会随着 for j 循环的进行而改变它们.

The issue is all in function closures. When the get data returns, your currentType is the last one because the for j loop ended already. So what you need to do is move the code starting from utility.getData to a separate method passing the parameters of the currentType and the seccondAttributeArray so the closure will contain them as parameters of the function and not change them as the for j loop progresses.

for (i = 0; i < $scope.myObjectArray.length; i++) { 
  var secondAttributeArray = []; 
  var currentType = $scope.myObjectArray[i];
  fillSecondAttributeArray($scope, secondAttributeArray, currentType);
 }

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