Extending a controller function within directive - angularjs

Question

I have a cancel function in my controller that I want to pass or bind to a directive. This function essentially clears the form. Like this:
app.controller('MyCtrl', ['$scope', function($scope){
var self = this;
self.cancel = function(){...
$scope.formName.$setPristine();
};
}]);
app.directive('customDirective', function() {
return {
restrict: 'E'
scope: {
cancel : '&onCancel'
},
templateUrl: 'form.html'
};
});
form.html
<div>
<form name="formName">
</form>
</div>
However, the $setPristine() don't work as the controller don't have access on the form DOM. Is it possible to extend the functionality of controller's cancel within the directive so that I will add $setPristine()?
Some suggested using jQuery to select the form DOM, (if it's the only way) how to do that exactly? Is there a more Angular way of doing this?

Answer 1

Since the <form> is inside the directive, the controller should have nothing to do with it. Knowing it would break encapsulation, i.e. leak implementation details from the directive to the controller.
A possible solution would be to pass an empty "holder" object to the directive and let the directive fill it with callback functions. I.e.:
app.controller('MyCtrl', ['$scope', function($scope) {
var self = this;
$scope.callbacks = {};
self.cancel = function() {
if( angular.isFunction($scope.callbacks.cancel) ) {
$scope.callbacks.cancel();
}
};
});
app.directive('customDirective', function() {
return {
restrict: 'E'
scope: {
callbacks: '='
},
templateUrl: 'form.html',
link: function(scope) {
scope.callbacks.cancel = function() {
scope.formName.$setPristine();
};
scope.$on('$destroy', function() {
delete scope.callbacks.cancel;
});
}
};
});
Use it as:
<custom-directive callbacks="callbacks"></custom-directive>
I'm not sure I am OK with this either though...