7_extend.md

Extending Request object

You can register custom properties and methods on Request object. This is typically done to accommodate objects that are bound to request lifetime such as database connections, sessions or caching. This lets you easily access that logic in one place. There also exist a mechanism to execute code on request completion by registering a callback in a view.

# examples/7_extend/extend.py
from japronto import Application


# This view accesses custom method host_startswith
# and a custom property reversed_agent. Both are registered later.
def extended_hello(request):
    if request.host_startswith('api.'):
        text = 'Hello ' + request.reversed_agent
    else:
        text = 'Hello stranger'

    return request.Response(text=text)


# This view registers a callback, such callbacks are executed after handler
# exit and the response is ready to be sent over the wire.
def with_callback(request):
    def cb(r):
        print('Done!')

    request.add_done_callback(cb)

    return request.Response(text='cb')


# This is a body for reversed_agent property
def reversed_agent(request):
    return request.headers['User-Agent'][::-1]


# This is a body for host_startswith method
# Custom methods and properties always accept request
# object.
def host_startswith(request, prefix):
    return request.headers['Host'].startswith(prefix)

app = Application()
# Finally register out custom property and method
# By default the names are taken from function names
# unelss you provide `name` keyword parameter.
app.extend_request(reversed_agent, property=True)
app.extend_request(host_startswith)

r = app.router
r.add_route('/', extended_hello)
r.add_route('/callback', with_callback)

app.run()

The source code for all the examples can be found in examples directory.