autosavingFileType
The document type to use for an autosave operation.
Declaration
nonisolated var autosavingFileType: String? { get }Discussion
This properties contains a string that identifies the document type for autosave files. The default implementation just returns the value provided by the fileType property. You can override this property and return nil to completely disable autosaving of individual documents (because the NSDocumentController object does not call the autosave(withDelegate:didAutosave:contextInfo:) 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 NSDocument method init(for:withContentsOf:ofType:), 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 fileType property with that type name, but that may not be the right thing to do if this property contains something other than fileType during document autosaving. If you override autosavingFileType, you probably need to override init(for:withContentsOf:ofType:) too, and make the override update fileType with the type of the actual document file, after invoking super. See TextEdit’s Document class for an example of how to do this.