Monthly Archive for September, 2008

Django Authorization from Flex/AIR via PyAMF

Published
by
Joel Hooks
on September 21, 2008
in AIR, actionscript, django, flex, pyAMF and python
. 6 Comments

Django views serve nicely as service end-points for Flex applications. Here are some notes on maintaining authenticated sessions between a Flex/Air/Flash application and your Django backend.

gateway.py

from pyamf.remoting.gateway.django import DjangoGateway
 
import myproject.myapp.views as views
 
gw = DjangoGateway({
    'login'                       : views.login_user,
    'logout'                     : views.logout_user,
})

views.py

import pyamf
from django.contrib import auth
from django.contrib.auth import authenticate, login, logout
from django.contrib.auth.decorators import login_required
from django.contrib.auth.models import User
 
try:
    pyamf.register_class( User,  'django.contrib.auth.models.User')
except ValueError:
    print "Classes already registered"
 
def logout_user(http_request):
    logout(http_request)
 
def login_user(http_request, username, password):
    user = authenticate(username=username, password=password)
    if user is not None:
        login(http_request, user)
        return user
    return None
 
@login_required
def registered_user_protected_function(http_request):
    return "You are a registered user."
 
@login_required
def staff_protected_function(http_request):
    if http_request.user.is_staff != True: return None
    return "You are staff."

from flex

var netConnection:NetConnection = new NetConnection();
netConnection.connect("http://mysite.com/gateway");
var responder:Responder = new Responder(loginResult, handleFault);
netConnection.call("login", responder, "username", "password")

The http_request carries a reference to the currently authenticated user throughout the session. This works for web based Flex application as well as AIR applications on the desktop. Note that I am using a try/except on the pyamf class registration calls. Because this is session based, the classes only need to be registered once. Without the trap, it throws a TypeError letting you know the registration has already taken place.

Django User Authentication Documentation
All of the various things you can do with authentication in Django. It is, of course, based mostly on the use of the very nice Django HTML template system. While those bits aren't handy to the likes of us, it is a good read either way.

pyAMF ByteArray example
This example shows the basic structure for setting up Django/Flex communication. It doesn't cover authentication, but covers a good bit of territory with examples in Flash and Flex.

Fabrication - Simplified PureMVC multicore modules (and more)

Published
by
Joel Hooks
on September 16, 2008
in components, design patterns, object oriented concepts and puremvc
. 1 Comment

One of the many reasons I love PureMVC is the community of highly intelligent, skilled, object-oriented (oriented) programmers that are constantly using the framework to build new and interesting utilities. This is a by-product of the very nature of PureMVC. Cliff architected the core framework in such a way that is is truly simple, providing a base from which to build new useful structures.

Fabrication, a new utility developed by Darshan Sawardekar is a shining example of this fact. He has taken the PureMVC multi-core apperatus, combined it with Cliff's Pipes utility, and created a wonderfully abstracted means for creating modular PureMVC applications. Not only does this simplify the connection of modules in your application and allow them to communicate seamlessly, but he provides a router/firewall metaphor for controlling the communication as well as undo/redo functionality.

Thanks Darshan, your efforts are appreciated. And as always, thanks Cliff for providing the base from which our community can build and contribute. Cheers.

Dynamic upload paths in Django

Published
by
Joel Hooks
on September 12, 2008
in django and python
. 0 Comments

I'm refactoring my VE:Session application a bit to the recently released Django 1.0. They have made some outstanding progress with the project overall, but there are enough things that are radically different to cause me to lose sleep searching for answers to small problems. I'd simply overlooked their NewForms branch when I was building the application, and now I am paying for it by standing well behind the curve. It is fun to learn new things though, so that is the upside I suppose.

Anyway, back to the refactoring. In addition to updating the project to the current Django trunk, I want to unify the application under Django. I am currently using SlideshowPro for my image CMS functionality. It is a fine product, but it obsfusicates the application and certainly makes it harder to deploy. This is compounded by the fact that I am using an older version of SSP. Django has some out of the box options for filing your uploads in a data structure. I really need something more customizable for the application though, and I was feverishly searching for a solution. The previous examples were complex hacks to get the job done. Which is fine, but they are now broken with the update to 1.0. D'oh. As luck would have it they are not neccesary any longer, and the same functionality can be added with a few simple lines that Scott Barnham was kind enough to demonstrate:

from django.db import models
 
def get_image_path(instance, filename):
    return 'photos/%s/%s' % (instance.id, filename)
 
class Photo(models.Model):
    image = models.ImageField(upload_to=get_image_path)

Awesome.

I've been knee deep in Java for the past few months, so it is really nice to get back into Python for a bit. With Django reaching a comfortable level of maturity, I see many more sleepless nights in my future.