Описание тега nsdocument
NSDocument is an abstract class that defines the interface for documents, objects that can internally represent data displayed in windows and that can read data from and write data to files. Documents create and manage one or more window controllers and are in turn managed by a document controller. Documents respond to first-responder action messages to save, revert, and print their data.
Conceptually, a document is a container for a body of information identified by a name under which it is stored in a disk file. In this sense, however, the document is not the same as the file but is an object in memory that owns and manages the document data. In the context of the Application Kit, a document is an instance of a custom NSDocument subclass that knows how to represent internally, in one or more formats, persistent data that is displayed in windows.
A document can read that data from a file and write it to a file. It is also the first-responder target for many menu commands related to documents, such as Save, Revert, and Print. A document manages its window’s edited status and is set up to perform undo and redo operations. When a window is closing, the document is asked before the window delegate to approve the closing.
NSDocument is one of the triad of AppKit classes that establish an architectural basis for document-based applications (the others being NSDocumentController and NSWindowController).