[Zope-dev] PROPOSAL: ZODB Relationships

[Max M]

roche@upfrontsystems.co.za wrote:

>We finally have a proposal out for ZODB relationships. This proposal
>presents an API for relationships, summarises ideas and contributions
>from a lot of people and was fuelled by the recent discussions about
>relationships on Zope3-dev and Zope-dev.
>
>    http://www.zope.org/Members/upfront/ZODBRelationships
>
>Your comments would be appreciated.
>

I have found the need for an API change. This:

    def get(obj):
      """
      Returns all objects related to this object as a set, or an empty set.
      """

Should really be changed to;

    def get(objects):
      """
      Returns all objects related to these object as a set, or an empty set.
      """

Frequently I need to get an aggregated list of relations. Ie. if I want 
to find all the student in a "department" I first find all the courses 
in that department, and then I find all the unique students. For things 
like that I have found that I very often use this idiom:

unique = {}
for obj in objects:
    result = self.relations.students_class.get(obj)
    for r in result:
        unique[tuple(r.getPhysicalPath())] = r
aggregated = unique.items()


It would be much easier to be able to pass a sequence and just use:

aggregated = self.relations.students_class.get(objects)

It is also consistent with the use of list and objects as passed to 
relate etc.


regards Max M