In 7. Operation Queues, under Waiting for completion, it says:
If you find yourself needing this method (OperationQueue waitUntilAllOperationsAreFinished), then you should set up a private serial DispatchQueue wherein you can safely call this blocking method.
My question is, how would I use waitUntilAllOperationsAreFinished – a method belonging to OperationQueue – by setting up a private serial DispatchQueue? Can I see a sample code?