Angular Directive, accessing the controller

1) Accessing required dependent directive controllers:

.directive('myDirRequiresNgModel', function(){
  return {
    restrict: 'A',
    require: 'ngModel',
    link: function(scope, iElement, iAttributes, ctrl){
      //ctrl is the ngModel controller
    }
  };
}]);

2) Accessing multiple required directive controllers

.directive('myDirRequiresNgModel', function(){
  return {
    restrict: 'A',
    require: ['ngModel','form'],
    link: function(scope, iElement, iAttributes, ctrl){
      //ctrl is the array of controllers [ngModel, ngForm]
    }
  };
}]);

3) Accessing parent required controller (living upwards in the dom tree

.directive('myDirRequiresNgModel', function(){
  return {
    restrict: 'A',
    require: '^form', // a '?^form' makes it optional
    link: function(scope, iElement, iAttributes, ctrl){
      //ctrl is the ngForm controller from the nearest parent with the directive
    }
  };
}]);

4) Accessing this controller the simple way

.directive('myDirRequiresNgModel', function(){
  return {
    restrict: 'A',
    controller: 'MyController',
    link: function(scope, iElement, iAttributes, ctrl){
      //ctrl is the MyController object
    }
  };
}]);

5) Accessing both MyController and ngModel (or any other directive controller)

.directive('myDirRequiresNgModel', function(){
  return {
    restrict: 'A',
    require: ['ngModel', 'myCtrl'],
    controller: 'MyController'
    link: function(scope, iElement, iAttributes, ctrl){
      //ctrl is [ngModel, MyController] 
    }
  };
}]).controller('MyController', function(){
  this.id = 'myCtrl';  // this is how it looks up the ctrl, apparently! 
});