Question

I want to create a simple Zope2 product that implements a “virtual” folder where a part of the path is processed by my code. A URI of the form

/members/$id/view

e.g.

/members/isaacnewton/view

should be handled by code in the /members object, i.e. a method like members.view(id='isaacnewton').

The Zope TTW Python scripts have traverse_subpath but I have no idea how to do this in my product code.

I have looked at the IPublishTraverse interface publishTraverse() but it seems very generic.

Is there an easier way?

Answer 1

Still the easiest way is to use the __before_publishing_traverse__ hook on the members object:

from zExceptions import Redirect


def __before_publishing_traverse__(self, object, request):
    stack = request.TraversalRequestNameStack
    if len(stack) > 1 and stack[-2] == 'view':
        try:
            self.request.form['member_id'] = stack.pop(-1)
            if not validate(self.request['member_id']):
                raise ValueError
        except (IndexError, ValueError):
            # missing context or not an integer id; perhaps some URL hacking going on?
            raise Redirect(self.absolute_url())  # redirects to `/members`, adjust as needed

This method is called by the publisher before traversing further; so the publisher has already located the members object, and this method is passed itself (object), and the request. On the request you’ll find the traversal stack; in your example case that’ll hold ['view', 'isaacnewton'] and this method moves 'isaacnewton' to the request under the key 'member_id' (after an optional validation).

When this method returns, the publisher will use the remaining stack to continue the traverse, so it’ll now traverse to view, which should be a browser view that expects a member_id key in the request. It then can do it’s work:

class MemberView(BrowserView):
    def __call__(self):
        if 'member_id' in self.request.form:  # Huzzah, the traversal worked!