how to access this inside an event receiver angular

问题

I was going over this tutorial to implement sending/receiving broadcast messages in my angular 1.5 app.

so inside a controller I have this:

  update(){
    this.$rootScope.$broadcast('language_changed');
  }

and in another controller I got this:

    $rootScope.$on('language_changed', function (event, data){
        this.updateStore();  <--- this here is undefined
    });

  }

  updateStore() {
      this.store = {
          ..
          language_id: this.LanguageService.get(),

        }
  }

I'm wondering how can I get hold of this inside the broadcast. This trick didn't work

回答1:

The answer that you provided is not a proper solution, you need to understand what are you doing, making hacks is not a solution. Please read the following article to get a basic knowledge about the difference between this and $scope this vs $scope

Important to know aswell concerning angular events:

$emit - Sends event up the angular three of scopes

$broadcast - Sends event down the angular three

Furthermore, please take a look at the following snippet: snippet

When you have two controllers, you don't need to both $broadcast the event from $rootScope and listen to it $on $rootScope, it can be simply listened to on a $scope level, $rootScope dependency injection is not needed. Check out the following:

app.controller('DemoCtrl', function($scope, $rootScope) {
  $scope.broadCastEvent = function() {
    $rootScope.$broadcast('language_changed');
  };
});

Let's say that we want to broadcast an event when user clicks a button. The event is sent down the angular three of scopes, so your controller that is listening to this event can listen it on scope level, without the $rootScope dependency injection, something like this:

app.controller('DemoCtrl2', function($scope) {
  $scope.$on('language_changed', function() {
   $scope.eventFired = !$scope.eventFired;
   });
})

The other case is when you want to $emit the event (send it up the angular three), then you would need to inject $rootScope to the controller that will be listening to that event, because only $rootScope can listen on a event that is being $emited from $rootScope. Check out the following:

Controller $emiting the event:

app.controller('DemoCtrl', function($scope, $rootScope) {
 $scope.emitEvent = function() {
  $rootScope.$emit('language_changed');
 };
});

Controller catching the event:

app.controller('DemoCtrl2', function($scope, $rootScope) {
  $rootScope.$on('language_changed', function() {
   $scope.eventFired = !$scope.eventFired;
 });
})

Try playing with the snippet a bit, look what happends if you want to $emit the event from $rootScope and try to catch it on the $scope level.

Hope this clarifies it a bit.

回答2:

solution was simple, using the javascript bind hack:

$rootScope.$on('language_changed', function (event, data){
    this.updateStore();
}.bind(this));  <-- bind makes the inner this same as outer this.. 😂

来源：https://stackoverflow.com/questions/48691233/how-to-access-this-inside-an-event-receiver-angular

标签

javascript

angularjs

eventemitter

angular1.6