Returns the document type that should be used for an autosave operation.
- macOS 10.4+
This properties contains a string that identifies the document type for autosave files. The default implementation just returns the value provided by the
file property. You can override this property and return
nil to completely disable autosaving of individual documents (because the
NSDocument object does not call the
autosave(with method of a document that has no autosaving file type). You can also override it if your app defines a document type that is specifically designed for autosaving, for example, one that efficiently represents document content changes instead of complete document contents.
Overriding this property can result in incorrect behavior during reopening of autosaved documents. The
init(for:, which is invoked during reopening of autosaved documents after a crash, takes two URLs, but only the type name of the autosaved contents file. The default implementation updates the
file property with that type name, but that may not be the right thing to do if this property contains something other than
file during document autosaving. If you override
autosaving, you probably need to override
init(for: too, and make the override update
file with the type of the actual document file, after invoking
super. See TextEdit’s
Document class for an example of how to do this.