Returns whether the receiver can concurrently write to a file or file package located by a URL, that is formatted for a specific type, for a specific kind of save operation.
- macOS 10.7+
The location of the file or package to which the document is written.
The string that identifies the document type.
The type of save operation.
false by default; subclasses can override to return
true, thereby enabling asynchronous writing.
The default implementation of this method returns
false. You are strongly encouraged to override it and make it return
true, after making sure your overrides of document writing methods can be safely invoked on a non-main thread, and making sure that the
unblock method is invoked at some appropriate time during writing.