https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/MemoryMgmt/Articles/mmPractical.html#//apple_ref/doc/uid/TP40004447-SW1
Use Accessor Methods to Set Property Values
Suppose you want to implement a method to reset the counter. You have a couple of choices. The first implementation creates the NSNumber instance with alloc, so you balance that with a release.