KVO notifications and threads

FROM : Jerry Isdale
DATE : Fri Jul 11 18:30:07 2008

I have an application whose data model (classes, shared Instances, 
etc) gets updated by various threads for calculations, network comms, 
etc.
Some of the application's Views use binding and KVO.  For example an 
NSTextField may get bound to SharedInstance.currentLattitude

It the property gets updated using KVO compliant code, on what thread 
is the NSTextField updated?

Possible answers include:
* thread that invokes the set method
* MainThread - because all UI updates should happen there.

Perhaps the KVO means that the View gets marked as needing an update 
in next update cycle, and thus we have a combination of these two 
answers:
* invoking thread marks the View for update
* MainThread does the update in its next graphics update cycle

Jerry Isdale
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