I'd like to use contexts when registering some observers, but have been unable to retrieve them, getting a "can't convert C/Objective-C value `0x2822731' of type `v' to Ruby object" instead. The following code, for example, will trigger the error class Subject attr_accessor :abc end class Observer def observeValueForKeyPath keyPath, ofObject:object, change:change, context:context context[0] end end subject = Subject.new observer = Observer.new subject.addObserver observer, forKeyPath:'abc', options:0, context:'a context' subject.setAbc 'some value' Is there a way to retrieve an observation context? Or is there an alternative way for observers to distinguish among multiple registrations for a given object/keyPath? Thanks, Ed