Thanks a lot!
But I already knew how to send it to the view, but I really need it in the controller.
Coz I need to set the height dynamically of ion-slide-box on slide change.
I also noticed something wrong with the directive... It gives me the height of the slide before data are loaded into it. 
I need the height after the slide is filled with the data I fetch from firebase. That makes it all more complicated I guess... 