NSArray property: copy or retain?

Question

According to this: NSString property: copy or retain?

For NSString/NSMutableString, copy is recommended.

How about NSArray/NSMutableArray?

Answer 1

If it is a problem when the underlying data changes, use copy. In fact, this is what you want most of the time, as changing data behind someone's back is a good source for bugs.

Note that copy will essentially just be a retain for an NSArray. Only when you throw an NSMutableArray in, there is more work involved.