打印View Hierarchy 和 ViewController Hierarchy

(lldb) expr -l objc -O -- [[[UIApplication sharedApplication] keyWindow] recursiveDescription]
(lldb) expr -l objc -O -- [[[[UIApplication sharedApplication] keyWindow] rootViewController] _printHierarchy]

-l objc -O -- 用於轉換 Swift to Objective-C context.

打印View Hierarchy 和 ViewController Hierarchy 很實用