AngularJS directive, ControllerAs, scope and vm property - angularjs

Question

Using Angular I created a directive like this:
angular
.module('my-module', [])
.directive('myDirective', function () {
return {
restrict: 'E',
templateUrl: currentScriptPath.replace('.js', '.html'),
scope: {
scenarios: '='
},
controller: MyDirectiveController,
controllerAs: 'vm',
bindToController: true,
replace: true
}
});
MyDirectiveController:
MyDirectiveController.$inject = ['$scope'];
function MyDirectiveController($scope) {
var vm = this;
vm.scenarios = $scope.scenarios;
}
My directive HTML template is this:
<div>{{vm.scenarios[0].name}}</div>
In my parent view HTML I'm using the directive this way:
<my-directive scenarios="vm.scenarios"></my-directive>
The parent controller has a property:
vm.scenarios = [] // could be [{ name : "test"}]
As the vm.scenarios of the parent controller gets set after an $http call it is not available when the vm.scenarios of the directive controller is bound to the $scope.scenarios and it doesn't get updated when the parents controller vm.scenarios gets populated eventually.
When adding this to my directives controller, it works but the solution seems wrong to me:
$scope.$watch('scenarios', function(newValue) {
if (newValue !== undefined) {
vm.scenarios = $scope.scenarios;
}
});

Answer 1

This is how you should define your directive controller:
MyDirectiveController.$inject = [];
function MyDirectiveController() {
// nothing here
}
You don't need to use $scope because you already bind to controller instance this. It means that scope config
scope: {
scenarios: '='
},
populates controller instance this object, not $scope object, and hence $scope.scenarios is undefined. With vm.scenarios = $scope.scenarios; in controller you just overwrite correct binding with undefined value.
Demo: http://plnkr.co/edit/lYg15Xpb3CsbQGIb37ya?p=preview