Question

When I’m setting a property with an object that is currently in a retained NSArray, will it only store the pointer (light-weight), or will it copy the contents to the property?

From what I know, it seems like it would only assign the pointer, but I’m not sure.

Also, under what circumstances would using *pointer = *otherPointer or the set methods (setDelegate, for instance) copy the value, instead of just passing the pointer, if any.
Shouldn’t it always just pass the pointer address?

Answer 1

It always passes the pointer, as you said. Unless you are specifically adding a de-referencing sign, this will always be the case.

However, when you add a property to a class, and set the setter to copy:

@property (nonatomic, copy) id obj;

When using the dot syntax or the setter, This will be translated to:

_obj = [otherObj copy];

Here, it will depend whether the object in question supports copying itself, or will it fall back to it’s super class NSObject or another intermediate class’s copy.

Moreover, Collection classes NSDictionary and NSArray do a shallow copy, as in they copy the references to their objects only, so you have two collections pointing to the same set of objects.