NSDocumentController is a class that controls a set of NSDocuments for an application. As an application delegate, it responds to the typical File Menu commands for opening and creating new documents, and making sure all documents have been saved when an application quits. It also registers itself for the NSWorkspaceWillPowerOffNotification. Note that NSDocumentController isn't truly the application delegate, but it works in a similar way. You can still have your own application delegate - but beware, if it responds to the same methods as NSDocumentController, your delegate methods will get called, not the NSDocumentController's.

NSDocumentController also manages document types and the related NSDocument subclasses that handle them. This information comes from the custom info property list ({ApplicationName}Info.plist) loaded when NSDocumentController is initialized. The property list contains an array of dictionarys with the key NSTypes. Each dictionary contains a set of keys:

• NSDocumentClass - The name of the subclass
• NSName - Short name of the document type
• NSHumanReadableName - Longer document type name
• NSUnixExtensions - Array of strings
• NSDOSExtensions - Array of strings
• NSIcon - Icon name for these documents
• NSRole - Viewer or Editor

You can use NSDocumentController to get a list of all open documents, the current document (The one whose window is Key) and other information about these documents. It also remembers the most recently opened documents (through the user default key NSRecentDocuments)..

You can subclass NSDocumentController to customize the behavior of certain aspects of the class, but it is very rare that you would need to do this.