i want to add the undo button in my iphone app, how can i do this ?

Question

i am using he quartz for drawing the image in my view and now i want to add the undo button in my toolbar button on myipad app.

what is code or any example of doing this.

Answer 1

Store the old state in a stack. When the undo button is pressed, pop the stack and restore the state. Disable the undo button when the stack is empty. Be careful not to run out of memory.

What constitutes "old state" is probably very specific to your application.

Answer 2

NSUndoManager has been available since iPhone OS 3.0

http://developer.apple.com/iphone/library/documentation/cocoa/reference/Foundation/Classes/NSUndoManager_Class/Reference/Reference.html

http://developer.apple.com/iphone/library/documentation/Cocoa/Conceptual/UndoArchitecture/Articles/iPhoneUndo.html