Learning from Django

Who am I?

• web app developer here in San Diego
• FreeBSD, PostgreSQL, mod_wsgi, Django, jQuery
• greybeard lisper at heart
• total Emacs junkie

Dorky things I do with my nerdy friends

I run Django San Diego and help run the San Diego Web Standards Group.

Merb and Django

What’s a merbivore anyway?

Couldn’t find a picture of your mascot

Learning from Django: Lesson #1

Don’t let Bryan Veloso unilaterally decide on your mascot.

Terminology

Merb and Django

AWESOME!

Lots in common

Merb team studied Django and other web frameworks

• modularity
• pluggability
• clean
• obvious
• 1.0 is serious business

Topics

• Slices & modularity
• Admin interface
• Generic views
• Syndication
• Local flavors
• Documentation
• Agnosticism & defaults

Merb Slices / Django Apps

Slices are awesome—embrace them!
This is your gateway to reusability heaven.

James Bennett's fourfold path (part 1)

• Do one thing, do it well
• Don't be afraid of multiple apps slices

Unix Philosophy

• do one thing
• do it well
• work together

AWESOME!

Ex. MerbAuth

Separate slices for

• authentication
• user management
• role management

Site as glue

• each piece of functionality in separate slice
• Site stitches slices together in distinctive way

Profusion of many slices

Even simple Django sites easily end up composed of a dozen apps or more!

It’s hard

import this

Namespaces are one honking great idea—let’s do more of those!

The fourfold path, cont.

• Write for flexibility
• Build to distribute slices are gems already!

Flexibility ≠ Monkeypatching

import this

Explicit is better than implicit.

Protocol-Oriented Programming

Explicitly expose how your slice operates in a controlled manner, so that your slice continues to work when such exposed bits are changed out from under you.

Think aliasing vs. public API.

ObLisp: MetaObject Protocol

AWESOME!

Other examples

• MerbAuth’s strategies
• User signup slice + custom user profile workflow

Slice-centric Development

• slices as the core way to develop merb apps

Inevitable end result: Pinax

This one goes to eleven.

Is this already upon us, in gluttonberg?

</slices>

Your router pwns

• SRSLY
• I hope urls.py looks more like this in the future

Admin interface

Generic CRUD admin UI you get for free

# admin.py
from django.contrib import admin
from djangosd.apps.blog.models import Post

admin.site.register(Post)

# urls.py
from django.conf.urls.defaults import *
from django.contrib import admin

admin.autodiscover()

urlpatterns = patterns('',
    ('^admin/(.*)', admin.site.root),
)

Autoadmin cont.

This is pretty much the awesomest thing ever…

but it’s thoroughly tied to particular ORM.

Generic Views

from django.conf.urls.defaults import *
from djangosd.apps.blog.models import Post

info_dict = {
    'queryset': Post.objects.all(),
    'date_field': 'published',
}

# ...

# ...

urlpatterns =
  patterns('django.views.generic.date_based',
    (r'^(?P<year>\d{4})/(?P<slug>[-\w]+)/$',
     'object_detail', info_dict),
    (r'^(?P<year>\d{4})/$',
     'archive_year', info_dict),
    (r'^$', 'archive_index', info_dict),
  )

N.B. “controller” vs. “view”

Syndication framework

from django.conf.urls.defaults import *
from djangosd.apps.blog.feeds \
    import LatestPosts, LatestComments

feeds = {'posts': LatestPosts,
    'comments': LatestComments,
}

urlpatterns = patterns('',
    (r'^feeds/(?P<url>.*)/$',
     'django.contrib.syndication.views.feed',
     {'feed_dict': feeds}),)

Feed objects

from django.contrib.syndication.feeds import Feed
from blog.models import Post

class LatestPosts(Feed):
    title = "Blah blah blah"
    link = "/"
    description = "Most recent posts blah."

    def items(self):
        return Post.objects.order_by('-published')[:10]

Local flavor

from django import forms
from django.contrib.localflavor.us.forms \
    import USSocialSecurityNumberField

class SomeForm(forms.Form):
    ssn = USSocialSecurityNumberField()

Also postal codes, phone numbers, region and city select boxes, etc.

Documentation

• two books in the pipeline: yay!
• new wiki: yay!
• RDoc ≠ documentation

Crucial to community growth

Agnosticism

• Merb ORM-agnostic
• (and template language-agnostic, and…)

Django’s branded defaults

• batteries included
• Where merb-stack is headed?
• e.g. jQuery, DataMapper, haml

Thank you

Questions?

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