$on and $broadcast in angular

Question

I have a footerController and codeScannerController with different views.

angular.module(\'myApp\').controller(\'footerController\', [\"$scope\", function($s         


        

Answer 1

First, a short description of $on(), $broadcast() and $emit():

• .$on(name, listener) - Listens for a specific event by a given name
• .$broadcast(name, args) - Broadcast an event down through the $scope of all children
• .$emit(name, args) - Emit an event up the $scope hierarchy to all parents, including the $rootScope

Based on the following HTML (see full example here):

    Broadcast 1
    Emit 1



    Broadcast 2
    Emit 2
    

        Broadcast 3
        Emit 3
        

        Broadcast Root
        Emit Root
    

The fired events will traverse the $scopes as follows:

• Broadcast 1 - Will only be seen by Controller 1 $scope
• Emit 1 - Will be seen by Controller 1 $scope then $rootScope
• Broadcast 2 - Will be seen by Controller 2 $scope then Controller 3 $scope
• Emit 2 - Will be seen by Controller 2 $scope then $rootScope
• Broadcast 3 - Will only be seen by Controller 3 $scope
• Emit 3 - Will be seen by Controller 3 $scope, Controller 2 $scope then $rootScope
• Broadcast Root - Will be seen by $rootScope and $scope of all the Controllers (1, 2 then 3)
• Emit Root - Will only be seen by $rootScope

JavaScript to trigger events (again, you can see a working example here):

app.controller('Controller1', ['$scope', '$rootScope', function($scope, $rootScope){
    $scope.broadcastAndEmit = function(){
        // This will be seen by Controller 1 $scope and all children $scopes 
        $scope.$broadcast('eventX', {data: '$scope.broadcast'});

        // Because this event is fired as an emit (goes up) on the $rootScope,
        // only the $rootScope will see it
        $rootScope.$emit('eventX', {data: '$rootScope.emit'});
    };
    $scope.emit = function(){
        // Controller 1 $scope, and all parent $scopes (including $rootScope) 
        // will see this event
        $scope.$emit('eventX', {data: '$scope.emit'});
    };

    $scope.$on('eventX', function(ev, args){
        console.log('eventX found on Controller1 $scope');
    });
    $rootScope.$on('eventX', function(ev, args){
        console.log('eventX found on $rootScope');
    });
}]);