Hello all,
I am trying to understand some method access capabilities, so that methods can only my accessed by objects of a certain class, NOT one of its subclasses. I had thought that this restriction could be done using (Access = private), but that seems to restrict any external calls to the method, NOT calls by objects belonging to the subclass. I also don't see (Access = ?className) working, since an object of the subclass will also belong to the current class.
If the above made sense, and you can help, great! If not, below is a more practical example.
I am attempting to solve the following type of problem. I have a hierarchy of classes and subclasses, and I want to determine the lowest level of this hierarchy that a given object might belong to. As a thought example: I have phylogeny classes in the class hierarchy:
life=>animals=>vertebrates=>mammals,
with numerous other branchings. I have some object with a number of properties, and at each level of the hierarchy I have methods that check whether we have enough information to classify the object to a lower level (such as looking for hasSpine and makesMilk). At some point, we may simply run out of information (filled properties) to further classify our object, so it may be stuck as a 'vertebrates' class object, rather than the lowest level 'mammals'.
In order to do this check, I am storing a list of subclasses in each class. The current class hands each listed subclass in turn all of the available properties, and subclass methods then determine whether the current class is a member of that subclass. If it is, the object is recast as that subclass. This procedure is then repeated until either we run out of branches to head down, or no branch reports that the object is a member (let's ignore multiple branches saying the object is a member, for now).
OK. So with the above story, I want to prevent 'vertebrates' objects from calling certain 'animals' methods, namely the method that asks "what are the subclasses I need to check". At the moment, I am stuck in a loop with one of two issues; either,
- I have no method defined at the sub-class level to overload the super-class methods. The object thus calls the super-class method for getSubclasses and winds up in a horrible loop (since it is checking the same subclasses again and again, and we already know the object is a member of at least one).
- I tried (Access = private), but that also blocks s = getSubclasses(obj) from working, since I am not calling the method with another method of that class, but with the object itself as the argument.
Now, there are some kludgey workarounds I can imagine: making sure I overload the super-class methods at EVERY level of the hierarchy, some more advanced use of 'isa' to make sure the object does NOT belong to one of the subclasses listed, etc. But I think there should be a way of doing this using access properties. Is there?
Cheers, -Dan
