Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
Class-based Views: patterns and anti-patterns
Search
Bruno Renié
June 04, 2012
Programming
9
1.6k
Class-based Views: patterns and anti-patterns
Bruno Renié
June 04, 2012
Tweet
Share
More Decks by Bruno Renié
See All by Bruno Renié
Visibility for web developers
brutasse
3
440
Decentralization & real-time with PubSubHubbub
brutasse
1
150
Deployability of Python Web Applications
brutasse
17
2.3k
Stop writing settings files
brutasse
21
2.5k
Packager son projet Django
brutasse
4
550
Staticfiles : tout ce qu'il faut savoir, rien que ce qu'il faut savoir
brutasse
4
540
Introduction to Django
brutasse
3
410
Other Decks in Programming
See All in Programming
dbt Pythonモデルで実現するSnowflake活用術
trsnium
0
270
AWS Step Functions は CDK で書こう!
konokenj
5
860
ABEMA iOS 大規模プロジェクトにおける段階的な技術刷新 / ABEMA iOS Technology Upgrade
akkyie
1
240
JAWS Days 2025のインフラ
komakichi
1
320
Datadog Workflow Automation で圧倒的価値提供
showwin
1
310
苦しいTiDBへの移行を乗り越えて快適な運用を目指す
leveragestech
0
1.2k
読まないコードリーディング術
hisaju
0
120
Datadog DBMでなにができる? JDDUG Meetup#7
nealle
0
160
kintone開発を効率化するためにチームで試した施策とその結果を大放出!
oguemon
0
330
⚪⚪の⚪⚪をSwiftUIで再現す る
u503
0
120
DevNexus - Create AI Infused Java Apps with LangChain4j
kdubois
0
130
Boos Performance and Developer Productivity with Jakarta EE 11
ivargrimstad
0
610
Featured
See All Featured
Why Our Code Smells
bkeepers
PRO
336
57k
Building Your Own Lightsaber
phodgson
104
6.2k
Visualization
eitanlees
146
15k
Responsive Adventures: Dirty Tricks From The Dark Corners of Front-End
smashingmag
251
21k
Designing Experiences People Love
moore
140
23k
VelocityConf: Rendering Performance Case Studies
addyosmani
328
24k
Making the Leap to Tech Lead
cromwellryan
133
9.1k
It's Worth the Effort
3n
184
28k
Optimizing for Happiness
mojombo
377
70k
StorybookのUI Testing Handbookを読んだ
zakiyama
28
5.5k
How to train your dragon (web standard)
notwaldorf
91
5.9k
Distributed Sagas: A Protocol for Coordinating Microservices
caitiem20
330
21k
Transcript
Bruno Renié djangocon.eu 2012 Class-based Views patterns & anti-patterns
New in Django 1.3 Better in Django 1.4
Controversy http://lukeplant.me.uk/blog/posts/djangos-cbvs-were-a-mistake/ http://www.boredomandlaziness.org/2012/05/djangos-cbvs-are-not-mistake-but.html
The view contract in Django
# Your code def view(request): return HttpResponse('yay') urlpatterns = patterns('',
r'^$', view) # Django callback, args, kwargs = resolve(request.path_info) response = callback(request, *args, **kwargs)
A view is a callable that takes a request and
returns a response
Deprecation function-based generic views are being deprecated function-based views aren't
going anywhere
Other class-based stuff
class Middleware(object): def process_request(self, request): ... Middleware
class PageAdmin(admin.ModelAdmin): def get_changelist(self, request, **kwargs): ... Admin
single instance shared across requests
from django.views import generic class Users(generic.ListView): ... users = Users.as_view()
CBV api
as_view()?
class View(object): @classonlymethod def as_view(cls, **init): def view(request, *args, **kwargs):
self = cls(**init) return self.dispatch(request, *args, **kwargs) return view
class View(object): @classonlymethod def as_view(cls, **init): def view(request, *args, **kwargs):
self = cls(**init) return self.dispatch(request, *args, **kwargs) return view Thread-safety self.request self.args self.kwargs
Declarative vs. imperative
ccbv.co.uk
(biased) usage tips
Keep urls.py for URL definition Decorate in views.py
from django.utils.decorators import method_decorator def cbv_decorator(decorator): def _decorator(cls): cls.dispatch =
method_decorator(decorator)(cls.dispatch) return cls return _decorator @cbv_decorator(login_required) class MyView(generic.ListView): pass Decorating
Decorating class MyView(generic.ListView): pass my_view = MyView.as_view() my_view = login_required(my_view)
Decorating from django.views.decorators.cache import cache_page class CacheMixin(object): cache_timeout = 60
def dispatch(self, *args, **kwargs): return cache_page(self.cache_timeout)( super(CacheMixin, self).dispatch )(*args, **kwargs) class CachedView(CacheMixin, ListView): cache_timeout = 100 @cyberdelia — https://gist.github.com/1231560
MRO Extend, don't override unless you're 100% sure of what
you're doing
class MyView(generic.FormView): def get_initial(self): initial = super(MyViews, self).get_initial() initial.update({ 'foo':
'bar', 'other': 'thing', }) return initial
Case studies
Form processing class MyView(generic.FormView): def get_form_kwargs(self): kw = super(MyView, self).get_form_kwargs()
kw['user'] = self.request.user return kw def form_valid(self, form): form.save() return super(MyView, self).form_valid(form)
Form processing class MyForm(forms.Form): def __init__(self, *args, **kwargs): self.user =
kwargs.pop('user') super(MyForm, self).__init__(*args, **kwargs) def save(self): # self‐contained, user is known
Nested navigation class Level1(generic.TemplateView): template_name = 'level_1.html' def get_context_data(self, **kwargs):
ctx = super(Level1, self).get_context_data(**kwargs) ctx['stuff'] = do_some_work() return ctx class Level2(Level1): template_name = 'level2.html' def get_context_data(self, **kwargs): ctx = super(Level2, self).get_context_data(**kwargs) ctx['other_stuff'] = level_2_work() return ctx
Drop-in features class CleverPaginator(object): paginate_by = 100 def get_count(self): raise
NotImplementedError def get_paginate_by(self, queryset): count = self.get_count() if count > self.paginate_by * 1.5: return self.paginate_by return count class CountryView(CleverPaginator, ListView): def get_count(): return self.country.num_people
Registration
django-registration is great, but… I want more template variables I'm
not using contrib.auth I want to send an SMS instead of an email …
Writing a custom backend is not as simple as subclassing
the default views from le_social.registration import views class Register(views.Register): form_class = SMSRegistrationForm def send_notification(self): ... Sane, easily overridable defaults pip install django-le-social
Settings
Does it have to be that global? Is it a
switch people will want to flip at any time? Could it be… a class attribute/method instead? I know, I'll add a setting
ACCOUNT_EXPIRES_IN from le_social.registration import views class Activate(views.Activate): expires_in = 3600
* 24 * 7 # 7 days
SOCIAL_AUTH_LOGIN_REDIRECT_URL SOCIAL_AUTH_BACKEND_ERROR_URL from le_social.twitter import views class Callback(views.Callback): def success(self,
auth): ... def error(self, message): ...
CBVs are great but don't use them for everything
class Handler500(generic.TemplateView): template_name = '500.html'
None
class View(object): def dispatch(self, request, *args, **kwargs): handler = getattr(self,
request.method.lower(), self.http_method_not_allowed) return handler(request, *args, **kwargs)
Fantastic API for shipping reusable views Good API for extending
and plugging features in existing code
As a FBGV replacement: more power, less simplicity Don't limit
yourself to Django's implementation. Use the base View and your creativity
@brutasse bruno@renie.fr