.. _handler_directive: ``handler`` ----------- The ``handler`` directive adds the configuration of a :term:`view handler` to the :term:`application registry`. Attributes ~~~~~~~~~~ ``route_name`` The name of the route, e.g. ``myroute``. This attribute is required. It must be unique among all defined handler and route names in a given configuration. ``pattern`` The pattern of the route e.g. ``ideas/{idea}``. This attribute is required. See :ref:`route_pattern_syntax` for information about the syntax of route patterns. The name ``{action}`` is treated specially in handler patterns. See :ref:`using_add_handler` for a discussion of how ``{action}`` in handler patterns is treated. ``action`` If the action name is not specified in the ``pattern``, use this name as the handler action (method name). ``factory`` The :term:`dotted Python name` to a function that will generate a :app:`Pyramid` context object when the associated route matches. e.g. ``mypackage.resources.MyResource``. If this argument is not specified, a default root factory will be used. ``xhr`` This value should be either ``True`` or ``False``. If this value is specified and is ``True``, the :term:`request` must possess an ``HTTP_X_REQUESTED_WITH`` (aka ``X-Requested-With``) header for this route to match. This is useful for detecting AJAX requests issued from jQuery, Prototype and other Javascript libraries. If this predicate returns false, route matching continues. ``traverse`` If you would like to cause the :term:`context` to be something other than the :term:`root` object when this route matches, you can spell a traversal pattern as the ``traverse`` argument. This traversal pattern will be used as the traversal path: traversal will begin at the root object implied by this route (either the global root, or the object returned by the ``factory`` associated with this route). The syntax of the ``traverse`` argument is the same as it is for ``pattern``. For example, if the ``pattern`` provided to the ``route`` directive is ``articles/{article}/edit``, and the ``traverse`` argument provided to the ``route`` directive is ``/{article}``, when a request comes in that causes the route to match in such a way that the ``article`` match value is '1' (when the request URI is ``/articles/1/edit``), the traversal path will be generated as ``/1``. This means that the root object's ``__getitem__`` will be called with the name ``1`` during the traversal phase. If the ``1`` object exists, it will become the :term:`context` of the request. :ref:`traversal_chapter` has more information about traversal. If the traversal path contains segment marker names which are not present in the ``pattern`` argument, a runtime error will occur. The ``traverse`` pattern should not contain segment markers that do not exist in the ``pattern``. A similar combining of routing and traversal is available when a route is matched which contains a ``*traverse`` remainder marker in its ``pattern`` (see :ref:`using_traverse_in_a_route_pattern`). The ``traverse`` argument to the ``route`` directive allows you to associate route patterns with an arbitrary traversal path without using a a ``*traverse`` remainder marker; instead you can use other match information. Note that the ``traverse`` argument to the ``handler`` directive is ignored when attached to a route that has a ``*traverse`` remainder marker in its pattern. ``request_method`` A string representing an HTTP method name, e.g. ``GET``, ``POST``, ``HEAD``, ``DELETE``, ``PUT``. If this argument is not specified, this route will match if the request has *any* request method. If this predicate returns false, route matching continues. ``path_info`` The value of this attribute represents a regular expression pattern that will be tested against the ``PATH_INFO`` WSGI environment variable. If the regex matches, this predicate will be true. If this predicate returns false, route matching continues. ``request_param`` This value can be any string. A view declaration with this attribute ensures that the associated route will only match when the request has a key in the ``request.params`` dictionary (an HTTP ``GET`` or ``POST`` variable) that has a name which matches the supplied value. If the value supplied to the attribute has a ``=`` sign in it, e.g. ``request_params="foo=123"``, then the key (``foo``) must both exist in the ``request.params`` dictionary, and the value must match the right hand side of the expression (``123``) for the route to "match" the current request. If this predicate returns false, route matching continues. ``header`` The value of this attribute represents an HTTP header name or a header name/value pair. If the value contains a ``:`` (colon), it will be considered a name/value pair (e.g. ``User-Agent:Mozilla/.*`` or ``Host:localhost``). The *value* of an attribute that represent a name/value pair should be a regular expression. If the value does not contain a colon, the entire value will be considered to be the header name (e.g. ``If-Modified-Since``). If the value evaluates to a header name only without a value, the header specified by the name must be present in the request for this predicate to be true. If the value evaluates to a header name/value pair, the header specified by the name must be present in the request *and* the regular expression specified as the value must match the header value. Whether or not the value represents a header name or a header name/value pair, the case of the header name is not significant. If this predicate returns false, route matching continues. ``accept`` The value of this attribute represents a match query for one or more mimetypes in the ``Accept`` HTTP request header. If this value is specified, it must be in one of the following forms: a mimetype match token in the form ``text/plain``, a wildcard mimetype match token in the form ``text/*`` or a match-all wildcard mimetype match token in the form ``*/*``. If any of the forms matches the ``Accept`` header of the request, this predicate will be true. If this predicate returns false, route matching continues. ``custom_predicates`` This value should be a sequence of references to custom predicate callables. Use custom predicates when no set of predefined predicates does what you need. Custom predicates can be combined with predefined predicates as necessary. Each custom predicate callable should accept two arguments: ``info`` and ``request`` and should return either ``True`` or ``False`` after doing arbitrary evaluation of the info and/or the request. If all custom and non-custom predicate callables return ``True`` the associated route will be considered viable for a given request. If any predicate callable returns ``False``, route matching continues. Note that the value ``info`` passed to a custom route predicate is a dictionary containing matching information; see :ref:`custom_route_predicates` for more information about ``info``. Alternatives ~~~~~~~~~~~~ You can also add a :term:`route configuration` via: - Using the :meth:`pyramid.config.Configurator.add_handler` method. See Also ~~~~~~~~ See also :ref:`views_chapter`.