Passing Controller Function to Directive

Below is an example of how to call a controller function from inside an AngularJS directive:

myApp.directive('myDirective', function () {
    return {
        scope: { controllerFunction: '&callbackFunction' },
        link: function (scope, element, attrs) {
            scope.controllerFunction({ arg: '123' });
        },
    }
});

And the markup:

<div ng-controller="MyCtrl as vm">
      <span my-directive callback-function="vm.theControllerFunction(arg)" ></span>
</div>

We can also call the controller function whenever a value in the directive changes. An example of such directive:

myApp.directive('observeValueChange', function () {
    return {
        scope: { controllerFunction: '&callbackFunction' },
        link: function (scope, element, attrs, ngModel) {
            attrs.$observe('theValue', function (newValue) {
                scope.controllerFunction({ arg: newValue });
            })
        },
    }
});

The markup:

<input type="text" ng-model="vm.myVariable" />
      <span observe-value-change the-value="{{vm.myVariable}}" callback-function="vm.theControllerFunction(arg)" ></span>

See the working example in Plunker.