I think it's because nil *is* pretty special--this is the equivalent of a NullPointerException or similar in other languages (even though in fact nil is an object like any other, it *is* usually a different type of *semantic* error on the part of the programmer than with any other class). UndefinedObject is also a pretty long class name, so it's nice to leave that out. But I would be all in favor of making it "nil did not understand #selector", to be more consistent but still concise.
On Fri, Jun 27, 2025, 3:00 PM Aik-Siong Koh <as...@askoh.com> wrote: > Why is UndefinedObject version of "did not understand" so different from > others? > It also inverts the object message paradigm. > Thanks > Aik-Siong Koh > > description > > "Returns a textual description of the exception (based on the > message instance variable). If message is nil, it returns the > defaultDescription instead." > > message ifNil: [ ^ self defaultDescription ]. > message lookupClass == UndefinedObject ifTrue: [ > ^ message selector printString , ' was sent to nil' ]. > > ^ 'Instance of ' , message lookupClass printString > , ' did not understand ' , message selector printString >
