[Grok-dev] object relationships

[Jeroen Michiel]

I'm still working on one, but I'm doing it in my free time (which is hard to
come by these days), so bear with me, please...

Vanderson Mota dos Santos wrote:
> 
> Sorry for ressurecting the topic, but please, a tutorial of Object
> Relationships is needed, because for now, object relationships are not so
> straightforward and fast to make as could/should be, IMHO.
> 
> Regards
> 
> 2009/2/13 Martijn Faassen <faassen at startifact.com>
> 
>> Hey,
>>
>> I'm glad the basics work now. I was able to encapsulate the choice
>> behavior quite nicely without too little code. The trick was to derive a
>> new RelationChoice field so that the relation is actually indexed
>> properly and so you can pass a source to it. The other trick was to
>> create a new source factory that you can easily supply with a list of
>> targets.
>>
>> Jeroen Michiel wrote:
>> [snip]
>> > I still have a small issue if I want to remove my app:
>> >  File
>> >
>> "c:\docume~1\jm\.buildout\eggs\z3c.relationfield-0.4.1-py2.4.egg\z3c\relationfield\event.py",
>> > line 36, in removeRelations
>> >     catalog = component.getUtility(ICatalog)
>> >  File
>> >
>> "C:\Docume~1\jm\.buildout\eggs\zope.component-3.4.0-py2.4.egg\zope\component\_api.py",
>> > line 207, in getUtility
>> >     raise ComponentLookupError(interface, name)
>> > ComponentLookupError: (<InterfaceClass
>> zc.relation.interfaces.ICatalog>,
>> '')
>> >
>> > It seems the catalog is unregistered before the objects are removed, or
>> > something of that nature...
>>
>> Yes, it must be some deregistration order issue. I've seen those before
>> in other contexts.. I think the issue could be fixed by placing some
>> fallback behavior in event.py so that if the catalog is missing things
>> will proceed without error. Send me a patch or remind me to look at it
>> again. :)
>>
>> > At least I can write a nice how-to now!
>>
>> Great!
>>
>> > BTW: I had already found a nicer way to use a regular choice field with
>> a
>> > relation than what I described before, but I'll put it in the how-to as
>> > well.
>>
>> I'd be interested in learning about this too.
>>
>> > Speaking of how-to's: I already made a how-to on zc.sourcefactory that
>> I
>> > submitted for reviewing, but it hasn't been reviewed yet. Do I need to
>> do
>> > anything more? Or is this no longer the way how-to's should be
>> submited?
>>
>> Oh, just make noise on this list when you have something to review, I
>> don't think we have people watching what there is to review...
>>
>> I'll look at it now. That looks like a very nice introduction, so I'll
>> publish it right away. Thanks very much for writing it, I think people
>> will be helped by this.
>>
>> Regards,
>>
>> Martijn
>>
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>>
> 
> 
> 
> -- 
> Vanderson Mota dos Santos
> 
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> 

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