应用程序代表之间的差异

Question

What is the difference between:

[[UIApplication sharedApplication] delegate]

and

UIApplicationDelegate

Answer 1

UIApplicationDelegate is a protocol definition, which means it's a set of methods an object that conforms to it should implement.

[[UIApplication sharedApplication] delegate] is the way you have to ask for application delegate of your currently running application. That delegate should conform to UIApplicationDelegate .