Class Based Views - untangling the mess

history

• lots of common patterns in view
• generic views - template, single object, list of objects, forms ...
• but generic views don’t allow logic insertion, limited config options ...
• so let’s go class based (released in Django 1.3, talked about since 1.0)

why bad reaction?

• confusion over purpose
• confusion over implementation choices - complexity necessary, but not obvious why
• ravioli code - nicely packaged, but internals opaque, steep learning curve
• bad docs

Purpose - 2 distinct but connected bodies of work

• class based views

  • class based analog of view
  • http verb based methods
  • get automatic code for free - OPTIONS, HEAD, HTTP 405 ...

• class based generic views

  • built on top of class based views
  • analogs of the old generic views
  • address limits of functional approach
  • requires learning to know how and where to extend

Implementation Choices

• django wiki page on Class Based Views - lots of discussion archived here

• what does class view mean?

  • (btw, admin is a class based view)
  • factory classmethod, returns function that invokes dispatch()
  • (could have done, urls.py could be either callable or class - but wanted to keep urls.py contract clear, as other things use that. trade off)

Ravioli

• goal: replace function-based generics with class-based generic

• end point - series of mixins

  • basic update view has 9 classes! wtf
  • but then create view reuses almost all of that
  • another single class change creates a JSON response instead of a template response

• allows for maximum reuse

• very flexible

• easy to add mixins

• BUT you need to grok it

• bad docs originally, but much better now, and need to decide about best practice

Next

• better docs
• decide on standard way of eg login required
• extend
• experiment with API - django’s admin?

Have we solved the wrong problem?

• multiple forms and formsets (see bug #18830 about FormCollection )
• conditional forms
• continuous scrolling, not pagination
• ajax support (eg in place editing)
• pjax
• multiple “actions” per page