NSOperationQueue designated thread

Question

I want to use an NSOperationQueue to dispatch CoreData operations. However, operation queue behavior is not always the same (e.g. it dispatches using libdispatch on iOS 4.0/OS 10.6 which uses thread pools) and a queue might not always use the same thread (as NSManagedObjectContext requires).

Can I force a serial NSOperationQueue to execute on a single thread? Or do I have to create my own simple queuing mechanism for that?

Answer 1

Can I force a serial NSOperationQueue to execute on a single thread? Or do I have to create my own simple queuing mechanism for that?

You shouldn't need to do either of those. What Core Data really requires is that you don't have two pieces of code making changes to a managed object context at the same time. There's even a note on this at the very beginning of Concurrency with Core Data:

Note: You can use threads, serial operation queues, or dispatch queues for concurrency. For the sake of conciseness, this article uses “thread” throughout to refer to any of these.

What's really required is that you serialize operations on a given context. That happens naturally if you use a single thread, but NSOperationQueue also serializes its operations if you set maxConcurrentOperationCount to 1, so you don't have to worry about ensuring that all operations take place on the same thread.