-[NSDocument displayName]
Returns the name of the receiver as displayed in the title bars of the document’s windows and in alert dialogs related to the document.
If the document has been saved, the display name is the last component of the directory location of the saved file (for example, “MyDocument” if the path is “/tmp/MyDocument.rtf”). If the document is new, NSDocument makes the display name “Untitled n,” where n is a number in a sequence of new and unsaved documents. The displayable name also takes into account whether the document’s filename extension should be hidden. Subclasses of NSWindowController can override windowTitleForDocumentDisplayName: to modify the display name as it appears in window titles.