How to do a DetailView in django 1.3?

I'm currently learning how to use the class-based views in django 1.3. I'm trying to update an application to use them, but I still don't uderstand very well how they work (and I read the entire class-based views reference like two or three times EVERY day).

To the question, I have an space index page that needs some extra context data, the url parameter is a name (no pk, and that can't be changed, it's the expected behaviour) and the users that don't have that space selected in their profiles can't enter it.

My function-based code (working fine):

def view_space_index(request, space_name):

    place = get_object_or_404(Space, url=space_name)

    extra_context = {
        'entities': Entity.objects.filter(space=place.id),
        'documents': Document.objects.filter(space=place.id),
        'proposals': Proposal.objects.filter(space=place.id).order_by('-pub_date'),
        'publication': Post.objects.filter(post_space=place.id).order_by('-post_pubdate'),
    }

    for i in request.user.profile.spaces.all():
        if i.url == space_name:
            return object_detail(request,
                                 queryset = Space.objects.all(),
                                 object_id = place.id,
                                 template_name = 'spaces/space_index.html',
                                 template_object_name = 'get_place',
                                 extra_context = extra_context,
                                )

    return render_to_response('not_allowed.html', {'get_place': place},
                              context_instance=RequestContext(request))

My class-based view (not working, and no idea how to continue):

class ViewSpaceIndex(DetailView):

    # Gets all the objects in a model
    queryset = Space.objects.all()

    # Get the url parameter intead of matching the PK
    slug_field = 'space_name'

    # Defines the context name in the template
    context_object_name = 'get_place'

    # Template to render
    template_name = 'spaces/space_index.html'

    def get_object(self):
        return get_object_or_404(Space, url=slug_field)

    # Get extra context data
    def get_context_data(self, **kwargs):
        context = super(ViewSpaceIndex, self).get_context_data(**kwargs)
        place = self.get_object()
        context['entities'] = Entity.objects.filter(space=place.id)
        context['documents'] = Document.objects.filter(space=place.id)
        context['proposals'] = Proposal.objects.filter(space=place.id).order_by('-pub_date')
        context['publication'] = Post.objects.filter(post_space=place.id).order_by('-post_pubdate')
        return context

urls.py

from e_cidadania.apps.spaces.views import GoToSpace, ViewSpaceIndex
urlpatterns = patterns('',
    (r'^(?P<space_name>\w+)/', ViewSpaceIndex.as_view()),
)

What am I missing for the DetailView to work?