Returns a file extension to append to the file URL of the document file being written.
- iOS 5.0+
A Uniform Type Identifier (UTI) that indicates the type of document (for example, PDF or HTML).
A constant that indicates whether the document file is being written the first time or whether it is being overwritten. See
A string to use as the file extension of the document file.
The default implementation queries Launch Services to obtain the file extension matching the file (document) type. You can override this method to return a file extension that is different from the default extension. The default implementation of the
save(to: method calls this method before it gets the document content and writes the document file to disk.