Quincey, Keary, thanks for the replies -
...
All worked fine, except that, when the new dictionaries are added
by clicking the add: button, the mutable array managed by the
controller is replaced with a new array (rather than inserting the
new dictionary in the original array). The new array has the
correct content, apparently having copied all the pre-existing
dictionaries from the old array.
This is correct. NSMutableDictionary implements
'setValue:forKey:' (as a convenience, to provide very basic KVC
compliance) but it doesn't implement any indexed accessors, so the
array is updated via this 'setValue:forKey:', which means that the
array is completely replaced.
If you look at:
http://developer.apple.com/documentation/Cocoa/Conceptual/KeyValueCoding/Concepts/SearchImplementation.html#/
/apple_ref/doc/uid/20000955-SW2
you'll see that case (1) doesn't apply, but case (2) does.
I confirmed that if subArray is promoted to an instance variable,
then add: will perform an insertion rather than creating a new
array (in fact I've used this a lot in the past). It seems that
having the array be part of a mutable compound object results in
creation of a new, copied array instead of an insertion.
Presumably you haven't overridden 'accessInstanceVariablesDirectly:'
to return NO in your "certain object", so now case (3) applies, and
that results in the array being updated instead of replaced.
The problem you've got is that you want "subArray" to behave like a
fully KVO compliant indexed property, but you haven't implemented it
as such.
I guess I was lulled into thinking it wouldn't require any coding,
since the array controller always did insertions when it was bound to
an instance variable. Now it makes sense that the dictionary behaves
differently from the object.
Thanks again,
Rick
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