#doesNotUnderstand: and #respondsTo: inconsistency

Ralph Johnson johnson at cs.uiuc.edu
Thu May 18 16:35:57 UTC 2006

On 5/18/06, von Löwis Martin <Martin.vonLoewis at hpi.uni-potsdam.de> wrote:
> Now, if the class defines #doesNotUnderstand: in order to understand
> more messages, this usage breaks unless respondsTo: is updated
> accordingly (which it never is, in Squeak).

You are right.  One of the problems with #doesNotUnderstand: is that
changing it changes part of an object's behavior, but not all of it.
An object that handles a message with it is probably not considered an
implementor of that message.  It is easy to hack #doesNotUnderstand:,
it is hard to  change all the behaviors of the object to be


More information about the Squeak-dev mailing list