Using functions from directive controller within link function of same directive

Question

Perhaps I have a fundamental misunderstanding of how directive controllers work, from what I understand they are used as a sort of API to be exposed to other directives & controllers. I am trying to get the controller and link function to communicate internally.

For example I would like to be able to set a variable via the controller function and then use it in the link function:

var app = angular.module('test-app', []);

app.directive('coolDirective', function () {
    return {
        controller: function () {
            this.sayHi = function($scope, $element, $attrs) {
                $scope.myVar = "yo"
            }
        },
        link: function(scope, el, attrs) {
            console.log(scope.myVar);
        }   
    }
});

How can I access myVar or sayHi within the link function? Or have I just missed the point completely?

Answer 1

Both controller's $scope (defined in the controller, not in the sayHi function) and link scope are the same. Setting something in the controller will be usable from the link or viceversa.

The problem you have is that sayHi is a function that is never fired so myVar is never set.

Since sayHi is not in the scope, you need a reference to the controller and to do it, you can add a fourth parameter like this:

link: function(scope, element, attr, ctrl) {}

Then you could do a ctrl.sayHi() (But again, those params of sayHi belongs to the controller function.)

If you ever need to require another controller and still wanting to use its own directive, then you will need to require it too. So if this coolDirective needs to access to the controller of notCoolAtAll you could do:

require: ['coolDirective', 'notCoolAtAll']

That will do the trick. The link function will receive then an array of controllers as the fourth param and in this case the first element will be coolDirective ctrl and the second one the notCoolAtAll one.

Here is a little example: http://plnkr.co/edit/JXahWE43H3biouygmnOX?p=preview