Question

I’m currently developing an iPhone app communicating via REST with a web server.

Each time the app starts it checks for remote data updates. If the data has not been loaded I start an async request in the app delegates applicationDidBecomeActive and show a modal progress view while the request is running. Some of my view controllers also need a data update which should be handled while the same progress view is visible and after the first request has finished.

What is the best approach to handle this scenario? Post a notification to the view controllers after the first request has finished and call back the delegate to dismiss the progress view?
Or is this considered a bad solution?

Best Regards

Carsten

Answer 1

Posting a notification should be used if the sender does not know anything about (should not depend on) the observers. For example, data object posts notification when it changes, so the visual objects connected to it could update themselves.

In your case you need to have a root object, the owner of your view controllers. It may be your Application Delegate or a subclass of a Navigation Controller. Since the owner knows about the view controllers, it can directly tell them to update when the request finishes.

Generally, do not send notifications between the owner and its dependants. Owners can directly call dependants’ methods. Dependants can have weak links to their owners and let them know when they update. If you need to make dependants independent on the owner’s class, define a delegate protocol.