Question

This is an IOS6 question.

I have an app that is calling a class (A) to check something. Then I want to call a class (B) to do something else
Is it possible to make sure process B doesn’t start before process A finishes?

At the moment, I just call one after the other in the RootVC.

Each is showing a modal view, and I only get to see B ..

[self performA];
[self performB];

Thanks

Answer 1

There are several tools for managing the order of execution of parts of your application available to you. However since you are presenting view controllers you have a couple of constraints; you don’t want to block the main thread (or else the app will become unresponsive) and you must perform UI actions on the main thread.

In this case the most common, and probably most appropriate, solution is to setup a callback to trigger action B when action A finishes.

The modal view controller presented as part of A might call a delegate when it has finished its task successfully. That delegate can then begin task B.

Alternately you might pass a block to A which A will execute when it finishes. That block can then perform task B.