(UITabBarController *)self.window.rootViewController;

Question

I've seen this declaration in a tutorial where someone is changing the appearance of the UITabBarController.

UITabBarController *tabBarController = (UITabBarController *)self.window.rootViewController;

What does the first part after the equal sign do? To be more specific, the

(UITabBarController *)

By the way, is there some kind of overview of which classes are relevant when changing the UI appearance? I'm having a hard time figuring out when to call what.

Thanks a lot!

Answer 1

这是一种类型转换 ：所述(T)value操作者强制从原始类型的显式类型转换value到新的类型T 。