Simon Strandgaard wrote:

 >
 >> Remember, since singleton class always exists for each object
 >> (virtually), 'class <<obj' is rather corresponds to class re-opening.
 >>
 >
 >
 > I am only little familiar with class re-opening..
 >

'class << obj' by itself simple changes the current scope to the 
instance's singleton class. It doesn't change neither the instance 
itself, nor its inheritance structure. So I don't think this action 
should be reflected by any callback action.

/kent