I want to get reference on BaseController from AppDelegate.
My MainMenu.xib’s hierarchy is

where BaseController is:
@interface BaseController : NSObject
I’m trying but I always get nil;
BaseController *base = (BaseController*)self.window.windowController;
Create an outlet for it in the app delegate and connect the controller to the outlet, as you would any other object (for example a button) in Interface Builder.
Then, in your app delegate, you can refer to it like this:
You don’t need a cast if you already have declared the outlet to be of class
BaseController.