Send class as variable inside a function

hi, I’m trying to create a class which handles the loading of different objects, what i wanna do is to let the user to use its own classes for loader (those small animations which are showed while the item is loade) now I don’t knwo the name of the class or something, how can I pass a class inside the constructor of my class andmake it work properly? and receive hte properties for that class too from teh user and make that my class transfers them into the class received, my main class would work like a bridge. Thanks.