- Add a ``custom_predicates`` argument to the ``Configurator``

  ``add_view`` method, the ``bfg_view`` decorator and the attribute
  list of the ZCML ``view`` directive.  If ``custom_predicates`` is
  specified, it must be a sequence of predicate callables (a predicate
  callable accepts two arguments: ``context`` and ``request`` and
  returns ``True`` or ``False``).  The associated view callable will
  only be invoked if all custom predicates return ``True``.  Use one
  or more custom predicates when no existing predefined predicate is
  useful.  Predefined and custom predicates can be mixed freely.

- Add a ``custom_predicates`` argument to the ``Configurator``
  ``add_route`` and the attribute list of the ZCML ``route``
  directive.  If ``custom_predicates`` is specified, it must be a
  sequence of predicate callables (a predicate callable accepts two
  arguments: ``context`` and ``request`` and returns ``True`` or
  ``False``).  The associated route will match will only be invoked if
  all custom predicates return ``True``, else route matching
  continues.  Use one or more custom predicates when no existing
  predefined predicate is useful.  Predefined and custom predicates
  can be mixed freely.

1 files changed, 21 insertions, 5 deletions

diff --git a/docs/designdefense.rst b/docs/designdefense.rst
index 7260ec1ce..ea5a072f8 100644
--- a/docs/designdefense.rst
+++ b/docs/designdefense.rst
@@ -404,11 +404,27 @@ request method was ``POST`` and that the remote user agent passed
 For more information about predicates, see
 :ref:`view_predicates_in_1dot1` and :ref:`route_predicates_in_1dot1`.
 
-Many "prebaked" predicates exist.  Use of only "prebaked" predicates,
-however, doesn't entirely meet Ian's criterion.  He would like to be
-able to match a request using a lambda or another function which
-interrogates the request imperatively.  This may become a feature in a
-later release.
+Many "prebaked" predicates exist.  However, use of only "prebaked"
+predicates, however, doesn't entirely meet Ian's criterion.  He would
+like to be able to match a request using a lambda or another function
+which interrogates the request imperatively.  In 1.2, we acommodate
+this by allowing people to define "custom" view predicates:
+
+.. code-block:: python
+   :linenos:
+
+   from repoze.bfg.view import bfg_view
+   from webob import Response
+
+   def subpath(context, request):
+       return request.subpath and request.subpath[0] == 'abc'
+
+   @bfg_view(custom_predicates=(subpath,)))
+   def aview(request):
+       return Response('OK')
+
+The above view will only match when the first element of the request's
+:term:`subpath` is ``abc``.
 
 .. _zcml_encouragement: