I am trying to use an array controller to bind to an array that I
manage, and it appears from the documentation that I need to have a
proxy object that responds to all the standard array methods, so I
created that, and if I have the array methods named along the lines of
the key binding, then at least my get method is being called (though I
still don't think that the array controller understands that it is an
array rather than an instance variable).
But I want to have this a generic array proxy, where it can be
configured to hold any array of data, so I have set it up with two
instance variables: the real array (NSMutableArray) and the key that
it has been configured to respond to (NSString). I have implemented
all the array methods for - (NSArray *)realArray, -
(id)objectInRealArrayAtIndex:(unsigned)theIndex etc. and then
implemented respondsToSelector: to return YES for any of the methods
it should respond to for the configured key, and
methodSignatureForSelector: to replace realArray with the actual key I
want to respond to, and forwardInvocation: to invokeWithTarget:self
now that the method signature has been rewritten. I think all that is
pretty straightforward, but... the key value stuff never calls
respondsToSelector: or methodSignatureForSelector: - it appears that
it must be using some of the objc stuff like objc_method_list or
something like that which is completely bypassing the dynamic side of
the method lookups, and instead I get thrown into the
valueForUndefinedKey:. Can someone confirm that it is bypassing the
dynamic method lookups?
If this is the case, then my generic proxy just isn't going to work,
but unless arrangedObjects has some special processing going on, I
would have thought that the KVC/KVO runtime must support dynamic
method lookup, because it must do it for the _NSControllerArrayProxy
class.
The other thing I don't fully understand is how the normal KVC methods
work out whether it is an array, set, or value at the other end of the
relationship. In my array controller subclass, when it asks for
valueForKey: I return my array proxy object, but the normal
valueForKeyPath method seems to think it is a value rather than an
array, and doesn't call the array methods. So if I override the
valueForKeyPath: method, I'm not sure what I should return, because if
I return [myArrayProxy mutableArrayValueForKey:key] then it thinks it
has an array rather than an array proxy, and starts sending messages
like "count" to it. But if I return the proxy object, it sends a
descriptionWithLocale: to it (which does actually go through the
respondsToSelector: method, so I know that is working) and then
complains that it can't create a number from an object, which seems to
be further proof that it thinks it's an object and not an array.
I would have thought that it was possible to do what I am trying to
do, but am now having second thoughts because of all these issues. Any
suggestions and/or sample code would be very welcome.
Regards
Gideon
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