1 __attribute__((objc_root_class)) 2 @interface Root { 3 Class isa; 4 } 5 @end 6 7 @interface A<T,U> : Root 8 @end 9 10 @interface B<T,U> : A<T,U> 11 typedef void (*BCallback)(T, U); 12 + (id) newWithCallback: (BCallback) callback; 13 @end 14