Calling controller function from directive using bindToController - angularjs

Question

I wrote a plunker to see how to use bindToDirective to isolate scopes and using directive controller to call main controller function, but, I am doing something wrong. Could you suggest?
This is the plunker: http://plnkr.co/edit/UJLjTmIiHydHr8qRzAsX?p=preview
Code sample:
.controller('Ctrl', function() {
var self = this;
self.func = function() {
console.log('In the controller function');
};
})
.directive('myDirective', [ function() {
var self = {};
self.link = function (scope, elem, attrs, ctrl) {
elem.bind('click', function () {
ctrl.ctrlFunc();
});
elem.addClass('fa fa-file-excel-o fa-lg');
};
return {
restrict: 'E',
scope: {},
controller: function () {
},
controllerAs: 'DirCtrl',
bindToController: {
ctrlFunc: '&'
},
link: self.link
};
}])
html sample to associate main controller function to directive:
<div ng-controller="Ctrl">
<my-directive ctrlfunc="Ctrl.func()"></my-directive>
</div>

Answer 1

You have a number of issues:
You need a hyphen in your directive argument name and you should be passing the function reference, not calling the function directly (with params):
<my-directive ctrl-func="ctrl.func"></my-directive>
Second, you are using alias syntax in your controller (var self = this;), but not in your template. You need to update it to the following:
<div ng-controller="Ctrl as ctrl">
<my-directive ctrl-func="ctrl.func"></my-directive>
</div>
Finally, pass down the function reference with two-way binding instead of with & since that passes down values for implicit evaluation.
bindToController: {
ctrlFunc: '='
},
See working plunkr

Answer 2

I'm not sure you need bindToController...
This version calls your Ctrl's function: http://plnkr.co/edit/Rxu5ZmmUAU8p63hR2Qge?p=preview
JS
angular.module('plunker', [])
.controller('Ctrl', function($scope) {
$scope.func = function() {
console.log('In the controller function');
};
}) angular.module('plunker', [])
.controller('Ctrl', function($scope) {
$scope.func = function() {
console.log('In the controller function');
};
})
.directive('myDirective', [ function() {
return {
template: '<pre>[clickme]</pre>',
replace: true,
restrict: 'E',
scope: {
target: '&'
},
link: function (scope, elem, attrs) {
elem.bind('click', function () {
var fn = scope.target && scope.target(scope);
fn && fn();
});
elem.addClass('fa fa-file-excel-o fa-lg');
}
};
}])
HTML
<div ng-controller="Ctrl">
<my-directive target="func"></my-directive>
</div>