-[MyClassName copyWithZone:] unrecognized selector sent to instance

Question

My application crashed with the reason:

-[MyClassName copyWithZone:] unrecognized selector sent to instance

I have two classes. Let

Answer 1

Your -setObj1: method is declared as copy, so it calls -copy on your Class1 object. -copy just calls -copyWithZone:nil. So you either need to implement the NSCopying protocol (which means implementing -copyWithZone:), or change your property from copy to retain.