adding methods to a class from interfaces.py

Hi all:

I am looking for an explanation for something I am seeing that I don't
understand.

I am working on: https://issues.roundup-tracker.org/issue2550923 to
add a new computed property type.

I defined a Computed class in hyperdb.py with an example computation
method:

    class Computed(object):
       # ... defines for  __init__, __repr__, register, sort_repr

      def message_count(self, nodeid, db):
          return len(db.issue.get(nodeid, 'messages'))

Using interfaces.py the user can add methods to this class that can be
called from the schema. In schema.py I have:


  from roundup.hyperdb import Computed

  issue = IssueClass(....

                   count = Computed(Computed.message_count),
                   filecount = Computed(Computed.fileCount),
                   hello2 = Computed(Computed.hello2),...
          )

Now I thought I could just modify interfaces.py with:


  from roundup.hyperdb import Computed

  # class Computed(object): also fails
  class Computed:

    def fileCount(self, nodeid, db):
        return len(db.issue.get(nodeid, 'files'))

    def hello2(self, nodeid, db):
        return "hello2"

similar to how methods can be added for rest
https://www.roundup-tracker.org/docs/rest.html#programming-the-rest-api

Then fileCount and hello2 can be used in schema.py.

Using this for Computed however fails claiming that FileCount and
hello2 do not exist. E.G.

   AttributeError: type object 'Computed' has no attribute 'fileCount'

when loading schema.py. The count/message_count property works fine as
expected.

I can use either subclassing or setattr to add methods to Computed:

   # subclass inherit from Computed 
   computed = hyperdb.Computed

   class Computed(computed):

      def hello2(self, nodeid, db):
          return "hello2"

   # replaced Computed so the hello2 method is available to schema.py etc.
   hyperdb.Computed = Computed


   # extend class using setattr
   def fileCount(self, nodeid, db):
       return len(db.issue.get(nodeid, 'files'))

   setattr(hyperdb.Computed, 'fileCount', fileCount)

so there is a method to extend the Computed class, but why doesn't
redeclaring the Computed class and defining methods there work?

Thanks for any ideas.

--
				-- rouilj
John Rouillard
===========================================================================
My employers don't acknowledge my existence much less my opinions.