[Grok-dev] schema.List returns a list, but is it persistent?

[Souheil CHELFOUH]

I disagree
This is not a flaw in schema.List
your usecase is to make it persist. But, it's the unique usecase of a form.
However, a simple list is persistent, just doesn't trigger an update warning
for the ZODB if modified.

2009/8/26 Sebastian Ware <sebastian at urbantalk.se>

> A bug in applyData when I come to think about it... so I filed it :)
>
> Mvh Sebastian
>
> On 26 aug 2009, at 17.36, Sebastian Ware wrote:
>
> > That is true, however I would definitely call that behaviour a bug in
> > schema.List. The assumption that only data manipulation is done with
> > applyData sounds risky. You could get some pretty creepy bugs...
> >
> > Anyway, I'll look into your suggestion.
> >
> > A suggestion is to change the behaviour of applyData so that it
> > returns PersistentList.
> >
> > Mvh Sebastian
> >
> > On 26 aug 2009, at 17.25, Leonardo Rochael Almeida wrote:
> >
> >> IIRC, It is only a problem if you try to modify the list itself
> >> directly (like appending to, or extending the list,  or removing or
> >> replacing items or slices in the list). schema.List returns a new
> >> list
> >> for every form submission, instead of trying to alter the old list to
> >> include the new items. This new list is assigned to the object during
> >> applyData, so it will be persisted correctly.
> >>
> >> On the other hand, it's very easy to create your own class that
> >> extends from schema.List to return your own datatype. IIRC you only
> >> have to override one attribute in the subclass, and it will receive
> >> the same widgets as the superclass unless you register differently or
> >> alter the implemented interfaces.
> >>
> >> Cheers, Leo
> >>
> >> On Wed, Aug 26, 2009 at 11:56, Sebastian
> >> Ware<sebastian at urbantalk.se> wrote:
> >>> Lists need to be implemented as PersistentList in order to be
> >>> automatically persisted to ZODB, however schema.List returns an
> >>> ordinary list and applyData seemingly stores this list as is. Isn't
> >>> this a big problem?
> >>>
> >>>    tags = schema.List(title=u"Content Tags",
> >>> value_type=schema.Choice(title=u"Content Tag",
> >>>           vocabulary='Content Tags'), default = [])
> >>>
> >>> Mvh Sebastian
> >>>
> >>>
> >>> _______________________________________________
> >>> Grok-dev mailing list
> >>> Grok-dev at zope.org
> >>> http://mail.zope.org/mailman/listinfo/grok-dev
> >>>
> >
> > _______________________________________________
> > Grok-dev mailing list
> > Grok-dev at zope.org
> > http://mail.zope.org/mailman/listinfo/grok-dev
>
> _______________________________________________
> Grok-dev mailing list
> Grok-dev at zope.org
> http://mail.zope.org/mailman/listinfo/grok-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.zope.org/pipermail/grok-dev/attachments/20090826/f31b569b/attachment.html