General/NSButton is a subclass of General/NSControl. Any General/NSControl has methods for setting and finding its state. Check the superclass (in this case, of General/NSButton) when looking for a method that you don’t see in the subclass with which you are working.
(the discussion that was here, which was about using bindings to try to validate a control from the contents of a string, was appended to General/ValidatingUserInterface)
According to the Cocoa User Interface Validation documentation at http://developer.apple.com/documentation/Cocoa/Conceptual/General/UIValidation/index.html: “The protocols General/NSUserInterfaceValidations and General/NSValidatedUserInterfaceItem provide a standard way to validate user interface items�that is, to set their state as appropriate for the current application context”.
Unfortunately, automatic user interface validation is provided only for menu items and toolbar items. General/HHValidatedButton implements interface validation in a General/NSButton subclass. It is a drop-in subclass of General/NSButton. It channels validation through validateButton: and validateUserInterfaceItem:. Available from: http://www.bernard-web.com/pierre/code.html