> Can we access to functions of a directive through the ng-click event for example ?

Yes. See https://github.com/geoadmin/mf-geoadmin3/blob/master/src/components/contextmenu/ContextMenuDirective.js#L115 and https://github.com/geoadmin/mf-geoadmin3/blob/master/src/components/contextmenu/partials/contextmenu.html#L4 for example.