Safer Block-based NSNotificationCenter API
I wanted to learn how Clang decides when to show a warning, so I did what any reasonable person would do and dove into its source. Retain cycle checking is performed during the semantic analysis phase.
Sema::checkRetainCyclesis an overloaded method responsible for these checks.[…]
In case of a message send, the compiler checks for retain cycles only when a selector looks like a setter, i.e., it starts with the word
addorset. This check is rather simplistic. A warning isn’t presented to the user when usingNSNotificationCenter, because the compiler doesn’t know the lifecycle of that object.
So he made a MCSNotificationController wrapper so that the compiler can detect the retain cycle. It also makes sure that you don’t register for the same notification more than once and automatically unregisters in -dealloc.
Previously: NSNotificationCenter With Blocks Considered Harmful, How Not to Crash #3: NSNotification.
