When does autorelease actually cause a release in Cocoa Touch?

Question

I understand you need to be careful with autorelease on iOS. I have a method that is returning an object it allocs which is needed by the caller, so in this situation -- as I understand it -- I need to send autorelease to the object in the callee before it returns.

This is fine, but once control returns to the phone (i.e. after my button click has been processed) it seems that the autorelease pool is released. I suspect this is how it is supposed to be, but I am wondering what is the best practice for this situation.

I have resorted to sending a retain message from the caller so that the object is not released and then explicitly releasing it in dealloc.

Is this the best approach?

Answer 1

The autorelease pool is typically released after each iteration of the run loop. Roughly, every Cocoa and Cocoa Touch application is structured like this:

Get the next message out of the queue
Create an autorelease pool
Dispatch the message (this is where your application does its work)
Drain the autorelease pool

What you describe is the expected behavior. If you want to keep an object around any longer than that, you'll need to explicitly retain it.