[Zope-CMF] Extending FTI.isConstructionAllowed

[Tres Seaver]

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Wichert Akkerman wrote:
> I have a use case where I need to put additional restrictions on object 
> creation, in particular I need to restrict the maximum depth of items 
> inside of a container of a specific type. The ideal place to put such a 
> restriction seems to be the isConstructionAllowed method on the FTI. 
> Currently this method is not very extensible, which leads to complicated 
> code in various FTI types.
> 
> I am considering to add an extension point here, something like this:
> 
> class ITypeConstructionFilter(Interface):
>      def __init__(fti, container):
>          """Adapt on the FTI of the object being created and the target 
> container"""
> 
>      def allowed():
>          """Check if construction is allowed."""
> 
> 
> current checks such as the workflow check that was added in CMF 2.2, or 
> the type constraint logic Plone has in ATContentTypes could be moved to 
> such an adapter. The standard isConstructionAllowed method could then 
> query all registered adapters to check if construction should be possible.
> 
> Does this sound sensible?

I'm not sure about querying all adapters:  I think it would be clearer
to query the one adapter whose name corresponds to the type name of the
FTI (the "query all" case leads to tricky / emergent behavior).


Tres.
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Tres Seaver          +1 540-429-0999          tseaver at palladion.com
Palladion Software   "Excellence by Design"    http://palladion.com
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