Returns a Boolean value that indicates whether the receiver reads multiple documents of the given type concurrently.
- macOS 10.6+
The string that identifies the document type.
false by default; subclasses can override to return
true, thereby causing documents of the specified type to be read concurrently.
NSDocument subclass can implement this method to return
true to enable loading of documents concurrently, using background threads. When this facility is enabled in this way,
init(contents executes on a background thread when opening files via the Open panel or from the Finder. This allows concurrent reading of multiple documents and also allows the app to be responsive while reading a large document.
The default implementation of this method returns
false. A subclass override should return
true only for document types whose reading is thread-safe, as described in Multicore Considerations. You should disable undo registration during document reading, which is a good idea even in the absence of concurrency.
If you are checking the current Apple Event for a search string, you should not enable concurrent document opening, because code handling a document opening triggered by an Apple Event cannot get the current Apple Event. This happens because the event is suspended until all documents are read to enable correct reporting of success or error.