Google SoC (KVO + Bindings)

[Chris Farber]

Hi everyone!

I'm the Summer of Code student working on Key Value Observing and  
Bindings for GNUstep.

As things currently stand, I have finished the implementation of  
KeyValueCoding (which I believe Nicola has just committed) and am  
about 80 to 90% done with KeyValueObserving.

When I started working, KeyValueObserving was already partially  
implemented. I have filled in most of the holes, including  
implementing the willChange... and didChange... methods to properly  
store information about the change and send the proper change  
dictionary in the notification, updating KVO to properly obey  
+setKeys:triggerChangeNotificationsForDependentKey:. I have also  
implemented the mutableSetValueForKey: and mutableArrayValueForKey:  
methods of KVC to return appropriate collection proxy objects and  
updated them to automatically do KVO notifying, according to Apple's  
documentation.

As I work, I've been taking a close look at Apple's implementations  
with GDB and modeling my own implementation accordingly. For example,  
I found that for mutableArrayValueForKey:, Apple uses special proxy  
objects such as NSKeyValueFastMutableArray,  
NSKeyValueSlowMutableArray, and NSKeyValueIvarMutableArray depending  
on the circumstance, all of which inherit from NSKeyValueMutableArray.

My remaining work on KVO is essentially to finish up creating the  
NSKeyValueObservationForwarder chain so it can notify observers of  
key paths and look at performance. After this, I'll begin working on  
implementing Bindings.

Chris Farber