A few days ago I stumbled across an excellent article on obj.io about debugging, titled Debugging: A Case Study. The article walks us through the workflow of fixing a bug that turned out to be an issue in UIKit, and contains a number of useful debugging tricks. There was one trick that I did not previously know about, and which turned out to be immediately useful - printing the view controller hierarchy.
Similar to how it’s possible to print the view hierarchy using the private
-[UIView recursiveDescription], on iOS 8+ it’s also possible to print the
view controller hierarchy using another private method:
By calling this method on a window’s root view controller, we can see the entire
view controller hierarchy for a window. This is especially useful in the debugger:
(lldb) po [[[UIWindow keyWindow] rootViewController] _printHierarchy] <UINavigationController 0x7fe295815c00>, state: appeared, view: <UILayoutContainerView 0x7fe29411a860> | <TPAInitialViewController 0x7fe294118150>, state: appeared, view: <UIView 0x7fe29411fc90>
If you have any cool and/or useful debugging tricks of your own, let me know on Twitter.