[Zope-dev] Namespaces, ZPublisher, DocumentTemplate question

[Dieter Maurer]

Andreas Kostyrka writes:
 > I've got a product that inherits from Folder, and creates
 > some magic "content" by overriding __bobo_traverse__.
 > 
 > Now I've got the problem that I cannot access the "magic" items from
 > within a DocumentTemplate like in <dtml-var special>.
 > 
 > The interesting thing is, that I've overloaded __getattr__ and
 > __getitem__, and it seems both are never called. (Actual code snippets
 > at the end)
 > 
 > So I'm wondering how DocumentTemplates (and say Page Templates) access
 > the items and properties?
 > 
 > Andreas
 > 
 > code snippet:
 >     def __getattr__(self,k,*args):
 >         r=Folder.Folder.__getattr__(self,k,*args)
 >         print "__getattr__(%r,%r)==%r" % (self,key,r)
This will not work as you expect!

     "__getattr__" is only called, when the normal lookup
     does not succeed.
     "Folder.__getattr__" is inherited from "Persistent"
     and will serve only very few attributes.
     For all others, you will get an "AttributeError", before
     you print anything.

     Furthermore, "__getattr__" takes only one (non-self)
     arguement. Your code above (with this strange "*args" code)
     will pass two. You will get a "TypeError" before you print
     anything.

 >     def has_key(self,key):
 >         r=Folder.Folder.has_key(self,key)
"Folder" implements the mapping interface only very partially.
It does not implement "has_key".

 > ...
 >     def __getitem__(self,key):
 >         print "__getitem__(%r,%r)" % (self,key)
 >         try:
 >             return Folder.Folder.__getitem__(self,key)
 >         except KeyError:
 >             try:
 >                 return self.__bobo_traverse__(self,None,key)
 >             except AttributeError:
 >                 raise KeyError,key
"__getitem__" is only called, when you explicitely use "instance[key]".


Dieter