iOS Why UIImage copyWithZone error before iOS4.1

[mikezang]

I found if I run my app before iOS4.1, the app will shutdown with error [UIImage copyWithZone:]: unrecognized selector sent to instance.

But it is no any problem on iOS 4.2, I don't why, can you explain to me and how can I avoid it?

 

[ulbador]

I don't think UIImage implemented NSCopying (by default) before 4.2. So, long story short, you can't without creating your own image subclass (which is how people have done it before now)