Philipp von Weitershausen wrote:
Derek Richardson wrote:
I sense that I'm missing the point here. Perhaps you can elaborate on what you mean when you say "use" and "collaboration." I usually know what those terms mean, but I'm not sure I am getting it in this context.

The paragraph definitely seems to miss the point, so let me speak code::

  class UUIDUtility(Contained, Persistent):

      def __init__(self):
          self.uuids = IOBTree.IOBTree()
          self.intids = OIBTree.OIBTree()

      def getObject(self, uuid):
          intid = self.intids[uuid]
          return getUtility(IIntIds).getObject(intid)

      def getUUID(self, object):
          intid = getUtility(IIntIds).getId(object)
          return self.uuids[intid]

I'm omitting several seatbelts and various functions to add/remove objects from the UUID utility, but I hope you'll get the idea.

With the composition approach, the actual utility class may be a little shorter than simply copying the whole thing, but I'll still have to copy and just change the names on a bunch of stuff in (IIntIds -> IUUIDs, IIntIdsQuery -> UUIDSQuery, etc). And I'll have to copy most of the tests.

It still seems to me that the best approach is:

class BaseIdUtility(Contained, Persistent):


    def getObject(self, id):
        return self.refs[id]()

    def getId(self, object):
        ... # 9 lines of code

    ... # registration functions and the like


class IntIdUtility(BaseIdUtility):

    implements(IIntIds) # marker

    def __init__(self):
        self.ids = OIBTree.OIBTree()
        self.refs = IOBTree.IOBTree()
        self.added_event = IntIdAddedEvent
        self.removed_event = IntIdRemovedEvent

    def _generateId(self):
        """Generates a unique integer id.
        ... # this is 8 lines of code


class UUIDUtility(BaseIdUtility):

    implements(IUUIDs) # marker

    def __init__(self):
        self.ids = OOBTree.OOBTree()
        self.refs = OOBTree.OOBTree()
        self.added_event = UUIDAddedEvent
        self.removed_event = UUIDRemovedEvent

    def _generateId(self):
        """Generates a RFC 4122 uuid.
        return uuid1()

The subclasses are pretty much complete as written here and the BaseIdUtility is just a minor abridgment of IntIds. This allows all the interfaces (other than the two empty markers and the events) to be reused between intids and UUIDs and most of the tests can be performed for both, as well.

We've talked a lot about the composition alternative to my idea, but we haven't talked about my idea much. What is suboptimal with the way I'm proposing, other than that it requires changing zope core? Or is that a good enough reason to not do it?


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