Various Objective-C extensions to existing types
- Collection - extensions to collection classes (arrays, dictionaries)
- Design Pattern - extensions for design patterns not present in vanilla Objective-C (abstract classses, singleton)
- Protocol - various extensions relating to protocols
- String - various extensions relating to string objects
- Notification - various extensions relating to the notification system
- Null - extensions involving testing for nil, handing nil method arguments, and returning nil instead of throwing a range exception
- KVC - various extensions relating to key value coding
- Value - extensions for converting one type to another, related type - substitutes for
+[NSSomeClass someObjectWithSomeOtherObject:] - Other/Misc - uncategorized extensions
NSObject (DeallocListener) and NSObject (zeroingWeakReferenceProxy) contain some serious runtime voodoo.