def before(action):
"""Decorator to execute the given action function *before* the responder.
Args:
action (callable): A function of the form
``func(req, resp, resource, params)``, where `resource` is a
reference to the resource class instance associated with the
request, and `params` is a dict of URI Template field names,
if any, that will be passed into the resource responder as
kwargs.
Note:
Hooks may inject extra params as needed. For example::
def do_something(req, resp, resource, params):
try:
params['id'] = int(params['id'])
except ValueError:
raise falcon.HTTPBadRequest('Invalid ID',
'ID was not valid.')
params['answer'] = 42
"""
def _before(responder_or_resource):
if isinstance(responder_or_resource, six.class_types):
resource = responder_or_resource
for method in HTTP_METHODS:
responder_name = 'on_' + method.lower()
try:
responder = getattr(resource, responder_name)
except AttributeError:
# resource does not implement this method
pass
else:
# Usually expect a method, but any callable will do
if callable(responder):
# This pattern is necessary to capture the current
# value of responder in the do_before_all closure;
# otherwise, they will capture the same responder
# variable that is shared between iterations of the
# for loop, above.
def let(responder=responder):
do_before_all = _wrap_with_before(action, responder)
setattr(resource, responder_name, do_before_all)
let()
return resource
else:
responder = responder_or_resource
do_before_one = _wrap_with_before(action, responder)
return do_before_one
return _before
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