Returns the nearest shared undo manager in the responder chain.
- iOS 3.0+
- tvOS 9.0+
By default, every window of an application has an undo manager: a shared object for managing undo and redo operations. However, the class of any object in the responder chain can have their own custom undo manager. (For example, instances of
UIText have their own undo manager that is cleared when the text field resigns first-responder status.) When you request an undo manager, the request goes up the responder chain and the
UIWindow object returns a usable instance.
You may add undo managers to your view controllers to perform undo and redo operations local to the managed view.