Updatings to the documentation for Pecan hooks.

This commit is contained in:
Ryan Petrello
2011-03-06 11:26:38 -05:00
parent 7e2883f03a
commit 1cbbae1ca7

View File

@@ -2,32 +2,29 @@
Hooks
=====
Pecan Hooks are a nice way to interact with the framework itself rather than
writing middleware.
Pecan Hooks are a nice way to interact with the framework itself without having to
write WSGI middleware.
There is nothing wrong with WSGI Middleware, and actually, it is really easy to
use middleware with Pecan, but it is rather hard (sometimes impossible) to have
access to Pecan's internals.
use middleware with Pecan, but it can be hard (sometimes impossible) to have
access to Pecan's internals from within middleware. Hooks make this easier.
Hooks offer four ways of dealing with a request:
* ``on_route``: called before Pecan attempts to route a request
* ``on_route``: called before Pecan attempts to route a request to a controller
* ``before``: called after routing but before processing the request
* ``before``: called after routing, but before controller code is run
* ``after``: called after a request has been processed
* ``after``: called after controller code has been run
* ``on_error``: called when a request generates an error
* ``on_error``: called when a request generates an exception
Implementation
--------------
They are very easy to plug into Pecan. In the below example we will go through
a simple hook that will gather some information about the request and then it
will print it out to ``stdout``.
In the below example, we will write a simple hook that will gather
some information about the request and print it out to ``stdout``.
Your hook needs to import ``PecanHook`` which will be used to inherit from.
This is how your hook file should look like::
Your hook implementation needs to import ``PecanHook`` so it can be used as a base class::
from pecan.hooks import PecanHook
@@ -35,41 +32,48 @@ This is how your hook file should look like::
def after(self, state):
print "\nmethod: \t %s" % state.request.method
print "response: \t %s" % state.response.status
print "\nresponse: \t %s" % state.response.status
The ``after`` method will be called after the request has been dealt with.
``on_route``, ``before``, and ``after`` are passed a shared state object which includes useful
information about the request, such as the request and response object, and which controller
was chosen by Pecan's routing.
If you save your file as ``my_hook.py`` you should be able to add it to your
application like this::
Attaching Hooks
--------------
Hooks can be attached in a project-wide manner by specifying a list of hooks
in your project's ``app.py`` file::
from application.root import RootController
from my_hook import SimpleHook
from my_hooks import SimpleHook
app = make_app(
RootController(),
hooks = [SimpleHook()]
)
We are passing the ``RootController`` of our application (make sure to replace
the bogus values with your own) and our ``SimpleHook`` goes into a list for the
``hooks`` parameter.
Hooks can also be applied selectively to controllers and their sub-controllers
using the ``__hooks__`` attribute on one or more controllers::
We are not displaying how the entire file should look like but showing what is
of interest to get a hook into Pecan.
from pecan import expose
from my_hooks import SimpleHook
class SimpleController(object):
__hooks__ = [SimpleHook()]
@expose('json')
def index(self):
return dict()
Running it
----------
Now that our ``SimpleHook`` is passed on, let's see what happens when we run
Now that our ``SimpleHook`` is included, let's see what happens when we run
the app and browse the application::
python start.py config
Serving on http://0.0.0.0:8080
pecan serve config.py
serving on 0.0.0.0:8080 view at http://127.0.0.1:8080
method: GET
response: 200 OK
``config`` is our configuration file that we pass on to ``start.py`` and as
soon as a request is served we see the information from our ``after`` method.