Hi Marian,
On Thu, Dec 8, 2011 at 7:50 AM, Mariano Martinez Peck <marianopeck@gmail.com
wrote:
Hi guys. When the finds a methodDict in nil during the method lookup, it sends #cannotInterpret: to the receiver, but starting the methodLookup in the superclass of the class whose method dict was nil. Example, if I have A subclass from B and B has the method dict in nil, if I sent #foo to an instance of A, it will send #cannotInterpret: to such instance but starting the method lookup (of the #cannotInterpret:) in B (the superclass).
Now, when sending #cannotInterpret: aMessage, it sends as parameter an instance of Message. The thing is that in the instVar "lookupClass" it puts the receiver's class. In this example, A. But when you are implementing #cannotInterpret: such info (the lookupClass) is already there, because you DO have the receiver (in self), so you could always do a "self class". In my case, for some proxies I am doing, I would need not the lookupClass, but the class whose methodDict was nil, in this case, B.
Not quite. It puts the lookup class in the lookupClass inst var. So if a super send invokes cannotInterpret: lookupClass will hold the superclass of the method in which the send occurred.
So, questions:
- Do I break something if I do this? Am I limiting the solution somehow?
it is not always true that I can get the lookupClass while doing "self class" ? is there someone using this hook of #cannotInterpret:?
I have no idea. But given the lookupClass it is a simple matter to walk the hierarchy starting at lookupClass, looking for the first nil methodDictionary. This will be the class at which cannotInterpret: was initiated. Isn't this enough?
- Ok, I know that I should send an instance of Message with something it
is not the lookupClass in the instVar 'lookupClass', but it is a lookupClass in some form ;)
Thanks in advance,
-- Mariano http://marianopeck.wordpress.com