当它被设置在函数内部$范围变量未定义 [英] $scope variable is undefined when it is set inside a function

问题描述

我在我的学习应用程序下面的示例code。服务做他的工作，并拉起一些数据出来由PHP生成使用JSON code页面，到目前为止，一切顺利。

I have the following example code in my learning app. The service does his job and pulls some data out of a page with json code generated by php, so far so good.

服务：

(function() {
    'use strict';

    angular
        .module('app.data')
        .service('DashboardService', DashboardService);

    DashboardService.$inject = ['$http'];
    function DashboardService($http) {

        this.getFormules = getFormules;

        ////////////////

        function getFormules(onReady, onError) {
            var formJson = 'server/php/get-formules.php',
                formURL  = formJson + '?v=' + (new Date().getTime()); // Disables cash

            onError = onError || function() { alert('Failure loading menu'); };

            $http
                .get(formURL)
                .then(onReady, onError);
        }

    }
})();

然后调用函数getFormules在我的控制器，并把所有数据里面我的$ scope.formuleItems和测试，如果一切成功和o不'... $ scope.formuleItems =未定义<！ / code> - 奇怪，因为我的看法是显示数据的

控制器的一部分：

    dataLoader.getFormules(function (items){

        $scope.formuleItems = items.data;

    });

    console.log('+++++++++++++++++', $scope.formuleItems); // gives undefined

我做的第一件事就是搜索计算器上到处寻找，如果别人有同样的问题，并且有：<一href=\"http://stackoverflow.com/questions/31371331/undefined-variable-inside-controller-scope-issue\">Undefined变量中控制器功能。

我知道有一些walkarounds对于这一点，我做我自己的研究，但直觉告诉我，这个（见下例）不是解决这个问题的最好办法。

I know there are some walkarounds for this, i've done my own research, but something tells me that this (see example below) isn't the best way to solve this problem.

的解决方法一：把$观赏控制器内的

$scope.$watch('formuleItems', function(checkValue) {
   if (checkValue !== undefined) {
     //put the code in here!
  }
}

甚至是：

if($scope.formuleItems != null) {}

控制器的其余部分是依靠$ scope.formuleItems。难道我真的把一切都变成了 $观看或如果？我可以承诺解决这一问题？我从来没有之前那么一些帮助将AP preciated。

The rest of the controller is relying on $scope.formuleItems. Do i really have to put everything into that $watch or if? Can i fix this with a promise? I never did that before so some help would be appreciated.

推荐答案

在code在回调

function (items){
    $scope.formuleItems = items.data;
}

异步评估。这意味着你首先开火的请求，然后JavaScript的继续执行，你的code线，因此，执行

is evaluated asynchronously. That means you first fire the request, then javascript keeps on executing your lines of code, hence performs

console.log('+++++++++++++++++', $scope.formuleItems); // gives undefined

此时回调尚未被调用，因为这需要一些时间，并且可以在任何时候发生。执行不停止对于这一点。
因此$ scope.formuleItems的价值仍然是不确定的，当然。

At this point the callback was not invoked yet, because this takes some time and can happen at any point. The execution is not stopped for this. Therefore the value of $scope.formuleItems is still undefined, of course.

之后 - 在未来的某些不限定的时间（可能几毫秒后）回调将被调用和$ scope.formuleItems的值将被改变。您需要登录您的回调函数的值INSIDE。

After that - at some not defined time in the future (probably a few milliseconds later) the callback will be invoked and the value of $scope.formuleItems will be changed. You have to log the value INSIDE of your callback-function.

您迫切要理解这个概念，如果你想在JavaScript中获得成功，因为这发生了一遍又一遍：）

You urgently have to understand this concept if you want to succeed in JavaScript, because this happens over and over again :)

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