Inheriting or sharing directive controller - angularjs

Question

I have two directives: A and B. They're very similar. I want directive B to inherit the controller in directive A.
In other words, the same function used for controller: in A's directive definition object needs to also be the controller: function used in B's directive definition object.
Aside from a copy/paste of the controller: function, how I use the same function in both A and B's definition?

Answer 1

Controllers are just regular JS functions, so, you can use prototyping:
function BaseController(){
this.commonFunct = function(){
...
}
}
function CtrlA(){
}
CtrlA.prototype = BaseController
function CtrlB(){
}
CtrlB.prototype = BaseController
this works with controllerAs syntax, when your controller is exposed to scope under some name, say ctrl. Then $scope.ctrl.commonFunct (more generic, works from any place of controller) or this.commonFunct (can be used in controller's instance methods, where this is controller itself) can be used to refer the function.
That works if you declare both controllers in one module as named functions. If they are declared in different modules, you can use mixin-like way with $controller:
// Base module
(function() {
'use strict';
angular.module('Base', []);
function BaseController($scope, <injectables>, that) {
that.commonFunct = function() {
};
}
angular.module('Base').controller('BaseController',
['$scope', '...', BaseController]);
})();
// Module that inherits functionality
(function() {
'use strict';
angular.module('Derived', ['Base']);
function DerivedController($scope, $controller, ...) {
$controller('BaseController', {
'$scope' : $scope,
...
'that' : this
});
// this.commonFunct is available
}
angular.module('Derived').controller('DerivedController',
['$scope', '$controller', '...', DerivedController]);
})();
MHO: I suggest to use named functions for declaring controllers / services and directives as it is more natural, JS way of doing things. Also, I like controllerAs syntax much as it helps to distinguish data, stored directly in scope (like $scope.data) with controller's methods (they all are stored in one scope's named object, like $scope.ctrl).

Answer 2

If I understand correct, you don't really want to inherit controllers. You want to use one controller in 2 different directives.
If that's the case, just declare the controller function, and pass it to both directive definition objects as a function or a string.