For a small university project, I need to write an application in Smalltalk which simulates an award ceremony. Here artists and bands can be nominated to win an award. However, an individual artist can also be a jury member to vote for a nominee.
To enforce the restriction of artists who are not in a jury to not be able to vote, I was thinking of dynamically add a Trait to each artist object once they have been added to a jury. This then allows me to deal with method class appropriately.
My question now is, is it possible to accomplish dynamically adding Traits to an object? I already looked at How can I add methods to a class at runtime in Smalltalk? but is not really what I am looking for.
Regards
UPDATE 1 After adding the method on the class side, this works. However, when I wish to assign an artist to a jury I write something like:
kurt_cobain juryMemberOf: aJury.
then in the method juryMemberOf I add the (voting)artist to a list (to keep track of all the jury's he is a member of):
juryList add: (VotingArtist from: self)
When I then inspect juryList I indeed see I added VotingArtist objects to the list. However, the original Artist object in my Workspace hasn't changed into a VotingArtist. Not sure if this is possible but, later on I need to have the ability to write:
kurt_cobain votesFor: justin_bieber.
At this point in time I get a MessageNotUnderstood for the method votesFor which is normal since kurt_cobain is still an Artist object.
That's very hacky. You're problem can be solved using classic inheritance (which I'm not going to detail here, since it's homework). An artist with voting rights is simply a subclass or Artist. When you want to give an artist voting rights, change the class, e.g. VotingArtist from: self, where VotingArtist is the subclass of Artist. #from: could be implemented as
VotingArtist class>>from: anArtist
^ self new copyFrom: anArtist