Cocoa - Return information from NSOperation

Question

I have an IPhone app that uses webservices to get data from a server. I\'m putting each call to the webservice in a NSOperation subclass so that it can be threaded. My questio

Answer 1

It depends on your application. How many of the operations do you expect to run concurrently? What are you doing with the result? Are results aggregated or do they need to display in the UI immediately?

Sending notifications on the main thread is fairly heavyweight. Depending on what you're doing with the result, you could choke up your UI. From a design perspective, are the objects that you would be sending from the notification something that the observing class should know about? It may make more sense to make changes to your model objects from the operation and have a controller object observe those changes instead.

You could use Key Value Observing but you must be careful. The observer observes in the same thread that the change occurs on, so you should not make UI changes directly when observing isFinished.

If the object is only owned and used by the operation, then yes, it should be safe to send at the end of main. It will be retained by the notification.