pecan/docs/0.0.1/source/hooks.rst

Hooks

Pecan Hooks are a nice way to interact with the framework itself rather than writing 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.

Hooks offer four ways of dealing with a request:

• on_route: called before Pecan attempts to route a request
• before: called after routing but before processing the request
• after: called after a request has been processed
• on_error: called when a request generates an error

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.

Your hook needs to import PecanHook which will be used to inherit from.

This is how your hook file should look like:

from pecan.hooks import PecanHook

class SimpleHook(PecanHook):

    def after(self, state):
        print "\nmethod: \t %s" % state.request.method
        print "response: \t %s" % state.response.status

The after method will be called after the request has been dealt with.

If you save your file as my_hook.py you should be able to add it to your application like this:

from application.root import RootController
from my_hook 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.

We are not displaying how the entire file should look like but showing what is of interest to get a hook into Pecan.

Running it

Now that our SimpleHook is passed on, 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
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.