How to extend another controller in Angularjs?

Question

Angular

Hello. I have two absolutely identical controllers.
The only difference is vm.postStatus = 'ready' and vm.postStatus = 'live';
How do I do:

angular.extend(this, $controller('feedController', {$scope: $scope, vm: vm}));

In this case, the methods are predefined, but vm.postStatus with a string is not. Tell me what am I doing wrong?