Why would you put a controller in a directive with AngularJS?

Question

I recently saw this example. It's the first time I have seen a controller inside a directive. Is this a normal thing to do. I thought you were supposed to keep these two in different areas for testability:

myModule.directive('myComponent', function(mySharedService) {
    return {
        restrict: 'E',
        controller: function($scope, $attrs, mySharedService) {
            $scope.$on('handleBroadcast', function() {
                $scope.message = 'Directive: ' + mySharedService.message;
            });
        },
        replace: true,
        template: '<input>'
    };
})

Answer 1

Generally, you'd use controllers in directives to be able to share them between directives, on an element. It allows for directives to comunicate between them easily.

See here for a great explanation of how this works: http://egghead.io/video/angularjs-directive-to-directive-communication/