How would that work? The refcount need to be on the pointee, not on the pointer.

saagarjha · on Nov 25, 2020

It’s stored in the isa pointer inside the object.

gpderetta · on Nov 25, 2020

thanks, it makes sense now.

For what I understand, the isa pointer is sorta-kinda similar to a vtable pointer in C++.

saagarjha · on Nov 26, 2020

Yep. It’s actually a pointer to the class instance for the object, which is a full object that contains more information than a typical vtable might, but it serves as a “type ID” that the runtime can use to dispatch on.