[Grok-dev] unique item in container question
cklinger at novareto.de
Tue Mar 17 05:53:08 EDT 2009
in zope3 there is a concept called NamedChooser. You can look here 
for the default implementation. Of course you can override the
NameChooser for your NewsContainer so you can check if the news item
There is an example in Philipp´s *Web Component Development with Zope3*.
Hope this helps
> I have a grok.AddForm wich adds a NewsItem in a NewsContainer. I try
> to write some kind of validation so I dont have duplicate news in the
> As I see I have 3 a few options:
> 1. Write an invariant in the NewsItem model where I check if the news
> is unique in the *container*. I don't see this as a good option
> because I have to explicitly refer to the container in side a model.
> 2. Write the validation in the Add grok.action. The idea is that just
> before adding the new item in the container I check if I have
> duplicates. This was easy to do.
> My problem is that I can't(or I don't know how to) return an error to
> the user from this place.
> @grok.action('Add event')
> def add(self,**data):
> ...... do some validation
> return None?
> Do you have any suggestions ?
> Thank you !
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