Controller parameter undefined in my link function

Question

I am trying to do something very simple using the controller parameter of the link function for my directive, but passed as "undefined". Can someone tell me what I am missing?

HTML:

    <div ng-app="myApp">
        <div ng-controller="SampleCtrl" my-form >
            <p> Click count: {{ count }} </p>               
        </div>  
    </div>

Javascript:

myApp.controller('SampleCtrl', function($scope){    
    $scope.count = 0;

    this.init = function(val) {
        $scope.count = val;
    }   
});


myApp.directive('myForm', function() {    
    var linkFn = function(scope, elem, attrs, ctrl) {

        ctrl.init(17); //Error here.  ctrl is undefined

        elem.bind('click', function() {
            scope.$apply(function(){                
                scope.count++;
            });
        });     
    };

    return linkFn;
});

Answer 1

It seems like my directive should use the directive definition object to return the link function and include the reference to the controller as the "controller" ddo parameter, for example:

myApp.directive('myForm', function() {

    var linkFn = function(scope, elem, attrs, ctrl) {

        ctrl.init("17"); //This now works, due to my return below


        elem.bind('click', function() {
            scope.$apply(function(){                
                scope.count++;
            });
        });     
    };

    return {
        controller: 'SampleCtrl',
        link:linkFn};
});

Answer 2

How Dan correctly asks in his comment on the accepted answer

- ? ?

, ctrl .

require: 'ngModel'

ng-controller, .

, , , .

myApp.directive('maxFileSize', function () {
    return {
        restrict: 'A',
        require: 'ngModel',
        link: function (scope, element, attrs, ctrl) {
            var maxSize = Number(attrs.maxFileSize);

            var sizeHandler = function () {
                if (element.get(0).files.length) {
                    var fileSize = element.get(0).files[0].size; // in bytes
                    if (fileSize > maxSize) {
                        //console.log('file size is more than ' + maxSize + ' bytes!');

                        ctrl.$setValidity("fileSize", false);
                    } else {
                        ctrl.$setValidity("fileSize", true);
                    }
                }
            };

            element.bind('change', sizeHandler);
        }
    };
});

Answer 3

, , , Plunk?