NSDocument is the base class for document-based applications in Cocoa and provides the core functionality for managing documents and windows. It integrates with NSWindowController to coordinate opening and closing documents and windows. NSDocument also manages document versions through integration with NSFileVersion.

8. NSDocumentController
NSDocument
NSWindowController

9. NSDocument
NSDocument

10. NSDocument
+ (BOOL)autosavesInPlace
{
return YES;
}

11. preservesVersions NO

17. NSDocument isInViewingMode
YES

18. NSWindow
•NSWindowWillEnterVersionBrow
serNotification
•NSWindowDidExitVersionBrowse
rNotification

19. NSFileVersion
NSDocument