[Zope3-Users] Container Constraints

[Marcus J. Ertl]

Hi!

I want to have container, witch should contain links and others 
containers of his own type! What I did is this in my interface-definition:

class ILinkContainer(IContainer):
    """Basic folder, containing only links and other link folders."""
   
    def __setitem__(name, object):
        """ Add an ITodo object. """

    __setitem__.precondition = ItemTypePrecondition(ILink, ILinkContainer)

But zope tells me:

NameError: name 'ILinkContainer' is not defined

I'm shure, he is right! It's a little bit of recursion at this place. 
But what to do?

Creating a marker interface? Something like:

class IMarker(IContainer):
    """ ... """

class ILinkContainer(IMarker):
    """Basic folder, containing only links and other link folders."""
   
    def __setitem__(name, object):
        """ Add an ITodo object. """

    __setitem__.precondition = ItemTypePrecondition(ILink, IMarker)


Should work, but why creating a Interface "for nothing"? Must be a 
better way!

And last but not least: Happy new Year!

Bye
   Marcus Ertl