How to use it in your application

Once the middleware is setup you are ready to use it. The middleware put a new key qc.statusmessage into the WSGI environment. This is a MessageList object to which you can add Message objects to. It basically is a list like object.

The Message object can be imported from the qc.statusmessage.message module.

Now if you want to store a statusmessage from within your WSGI application you do the following:

from qc.statusmessage.message import Message

...


def some_view(environ):
    ...

    msg = Message(u"Your order has been placed.")
    environ['qc.statusmessage'].append(msg)

    ...

The middleware will then automatically take care of the message and serialize it to the cookie.

In the next request (which might happen after a redirect) you might want to display this message again to the user. It will be again available in the MessageList object store under the qc.statusmessage key in the WSGI environment:

def other_view(environ):
    msgs = environ['qc.statusmessage']
    if len(msgs):
        msg = msgs.pop()

        text = msg.msg

        ... somehow display the msg ...

As you can see the actual message text is stored in the msg attribute of the Message object. Moreover you should use the pop() method of the MessageList in order to remove this message from the list. That way it will not be displayed again next time because it won’t be serialized back to the cookie.

As you can also see from the example you can store more than one status message. It simply behaves like a list. What is still in the list on egress will be serialized back to the cookie. If no Message object is left in the MessageList object then the cookie will be deleted.

Storing additional data inside the message

Sometimes you need to store some more data about a message, e.g. you want to store whether it’s just an informational message, some warning or some error. You can do this simply by passing more paramaters into the Message object:

from qc.statusmessage.message import Message

INFO = 0
ERROR = 1
WARNING = 2


def some_view(environ):
    ...

    msg = Message(u"Your order has been placed.", type_ = INFO)
    environ['qc.statusmessage'].append(msg)

    ...

In the next request you can simply use attribute notation to retrieve the additional information again:

msg = environ['qc.statusmessage'].pop()
t = msg.type_

You can store any data as long as it does not exceed the maximum size of the cookie and can be serialized using JSON.