Release method for Objective-C

I have a class that keeps a count of all instances. It increases the count when an instance is allocated and needs to decrease it when the object is deallocated. Knowing when the object is allocated is easy, this can be done in the constructor. How do I know when the object is deallocated?

With the JVM I can override finalize. But on iOS, it is never called. Is there a common way to do this or an Objective-C way?