Parametrized apps for Django

abstract.py

class AbstractMixin(object):
    _classcache = {}

    @classmethod
    def contribute(cls):
        return {}

    @classmethod
    def construct(cls, *args, **kwargs):
        attrs = cls.contribute(*args, **kwargs)
        attrs.update({
            '__module__': cls.__module__,
            'Meta': type('Meta', (), {'abstract': True}),
        })
        key = (args, tuple(kwargs.items()))
        if not key in cls._classcache:
            clsname = ('%s%x' % (cls.__name__, hash(key))) \
                    .replace('-', '_')
            cls._classcache[key] = type(clsname, (cls, ), attrs)
        return cls._classcache[key]

example_models.py

from yourapp import factories

class MyCategory(factories.CategoryFactory.construct()):
    pass

class MyProduct(factories.ProductFactory.construct(category=MyCategory)):
    pass

example_urls.py

from django.conf.urls.defaults import patterns, include

from . import models

urlpatterns = patterns('',
    url('^my-app/$', include('yourapp.urls'), {'product_model': models.MyProduct}),
)

factories.py

from django.db import models

from . import abstract

class CategoryFactory(models.Model, abstract.AbstractMixin):
    name = models.CharField(max_length=100)

    class Meta:
        abstract = True

    def __unicode__(self):
        return self.name

class ProductFactory(models.Model, abstract.AbstractMixin):
    name = models.CharField(max_length=100)

    class Meta:
        abstract = True

    @classmethod
    def contribute(cls, category):
        return {'category': models.ForeignKey(category)}

    def __unicode__(self):
        return u'%s / %s' % (self.category, self.name)

urls.py

from django.conf.urls.defaults import patterns, url

from . import views

urlpatterns = patterns('',
    url('^(?P<id>\d+)/$', views.details),
)

views.py

from django.shortcuts import get_object_or_404
from django.views.generic.simple import direct_to_template

def details(request, product_model, id, template='example/details.html'):
    product = get_object_or_404(product_model, id=id)
    return direct_to_template(request, template, {'product': product})