SingletonClass* SingletonClass::attach(STATE, Object* obj, Class* sup) {
SingletonClass *sc;
sc = state->memory()->new_object_enduring<SingletonClass>(state, G(klass));
sc->init(state);
sc->attached_instance(state, obj);
sc->setup(state);
if(kind_of<PackedObject>(obj)) {
sc->set_type_info(state->memory()->type_info[Object::type]);
} else {
sc->set_type_info(obj->klass()->type_info());
}
sc->set_packed_size(obj->klass()->packed_size());
sc->packed_ivar_info(state, obj->klass()->packed_ivar_info());
/* The superclass hierarchy for singleton classes lives in parallel to
* that of classes. This code ensures that the superclasses of singleton
* classes are also singleton classes.
*/
if(SingletonClass* already_sc = try_as<SingletonClass>(obj)) {
/* If we are attaching a singleton class to something that is already a
* SingletonClass, make the singleton class's superclass be the attachee's
* superclass. klass and superclass are both singleton classes in this
* case.
*/
sc->klass(state, sc);
Class* super = already_sc->true_superclass(state)->singleton_class_instance(state);
sc->superclass(state, super);
super->track_subclass(state, sc);
} else {
/* If we are attaching to anything but a SingletonClass, the new
* singleton class's class is the same as its superclass. This is where
* the superclass chains for singleton and non-singleton classes
* diverge. If no superclass argument was provided, we use the klass we
* are replacing.
*/
if(!sup) {
sup = obj->klass();
}
/* Tell the new SingletonClass about the attachee's existing hierarchy */
Class* super_klass = Class::real_class(state, sup)->klass();
sc->klass(state, super_klass);
sc->superclass(state, sup);
sup->track_subclass(state, sc);
}
/* Finally, attach the new SingletonClass */
obj->klass(state, sc);
return sc;
}
SingletonClass* SingletonClass::create(STATE, Object* obj) {
SingletonClass *sc;
sc = state->memory()->new_object_enduring<SingletonClass>(state, G(klass));
sc->init(state);
WeakRef* weakref = WeakRef::create(state, obj);
sc->object_reference(state, weakref);
sc->setup(state);
return sc;
}
