我需要改变的 this.usernamevalid 通过调用函数的变量范围内的 checkusername ，这个功能是从这样的观点引发的值：

I need to change the value of the this.usernamevalid variable in the scope via a function called checkusername, this function is triggered from the view like this:

register.jade：（NG-控制器=控制器为txt）

register.jade: (ng-controller="controller as txt")

input(type="text", ng-model="formData.username",ng-blur="txt.checkusername('username',formData.username);" )

和功能的 checkusername 是：

regController.js

 ngApp.controller('controller', Main );

    function Main(){
         //I need to set this variable to true;
         this.usernamevalid = false;




         //In the View, I trigger this function
        this.checkusername = function(param, val) {

            if (val != undefined) {
                $http.get('http://localhost:3000/users?param='+param+'&val='+val)
                .then(function(response){
                    var size = response.data.length;
                    switch (param) {
                        case 'username':
                            if (size>0) {
                                //The user exist (DOES NOT WORK)
                                this.usernamevalid = true;
                            } else {
                                //The user don't exist (DOES NOT WORK)
                                this.usernamevalid = false;
                            }
                            break;
                            default:
                                console.log('Field undefined, STOP');
                    }
                }, function(response){
                    alert(response + "(error)");
                });
            }


        }

}

我尝试使用一个回调函数，但结果是一样的，我不能修改的结果 this.usernamevalid ，因为这不是定义。

推荐答案

基本上这个中的 $ http.get 函数。然后是不一样的这个控制器上下文的。

Basically the this inside the $http.get function .then is not the same this of your controller context.

所以，你应该在你的控制器函数创建一个变量如下图所示。

So you should create a variable in your controller function like below.

var vm = this;

这将使你的使用控制器随处可见这种背景 VM 变量。只需更换这个与 VM 无论你使用这个

Which will make your this context available everywhere in controller using vm variable. Just replace this with vm wherever you have used this

code

ngApp.controller('controller', Main);
   function Main() {
     var vm = this; //created local variable which will have this reference.
     //I need to set this variable to true;
     vm.usernamevalid = false;
     //In the View, I trigger this function
     vm.checkusername = function(param, val) {
       if (val != undefined) {
         $http.get('http://localhost:3000/users?param=' + param + '&val=' + val)
           .then(function(response) {
           var size = response.data.length;
           switch (param) {
             case 'username':
               if (size > 0) {
                 //The user exist (DOES NOT WORK)
                 vm.usernamevalid = true;
               } else {
                 //The user don't exist (DOES NOT WORK)
                 vm.usernamevalid = false;
               }
               break;
             default:
               console.log('Field undefined, STOP');
           }
         }, function(response) {
           alert(response + "(error)");
         });
       }
   }
 }

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