Better Django Views

A short look at good and bad patterns in Django Views

Transcript

1. BETTER DJANGO VIEWS akoumjian@gmail.com @akoumjian github.com/akoumjian Wednesday, June 26, 13
2. A GOOD VIEW 1. Encapsulates the Request / Response Cycle 2. Composed of Reuseable Bits (DRY) 3. Easy to Debug & Modify http://wallpaperswide.com/kitzbuhel_mountain_view_austria_europe-wallpapers.html Wednesday, June 26, 13
3. FUNCTIONAL VIEW Wednesday, June 26, 13
4. FUNCTIONAL IMPROVED Wednesday, June 26, 13
5. CLASS BASED VIEWS Inheritance encourages DRY / Reusable Code Wednesday, June 26, 13
6. CLASS BASED VIEWS Clean Delegation Declarative! Wednesday, June 26, 13
7. That looks Great! ...So what’s the problem? Wednesday, June 26, 13
8. • Obscure the Request / Response Cycle • Not particularly Reuseable / DRY • Hard to Debug and Harder to Modify Generic Views == Bad Patterns Wednesday, June 26, 13
9. An Example: UpdateView Looks Harmless... ...Let’s see what happens when we post Wednesday, June 26, 13
10. An Example: UpdateView Look for post() in inherited Classes Okay, what’s super calling? It’s somewhere... in here: Wednesday, June 26, 13
11. An Example: UpdateView Aha! Inside ProcessFormView Wednesday, June 26, 13
12. An Example: UpdateView To modify, we have to copy each parent function and insert into our override method Wednesday, June 26, 13
13. An Example: UpdateView Altering response data after is_valid() requries overriding 2 methods Wednesday, June 26, 13
14. A GOOD VIEW 1. Encapsulates the Request / Response Cycle 2. Composed of Reuseable Bits (DRY) 3. Easy to Debug & Modify http://wallpaperswide.com/kitzbuhel_mountain_view_austria_europe-wallpapers.html Wednesday, June 26, 13
15. Option 1: Better CBV Write your methods to be atomic Always return your response in top level method Wednesday, June 26, 13
16. Option 2: Pipeline Views I wanted to take things a step further. * Easy to debug any point of the request / response cycle * Easy to insert, update, change the order of operations * Reuse lots of pre-made methods without inheritance / mixin hell Wednesday, June 26, 13
17. Option 2: Pipeline Views An Example Pipeline Wednesday, June 26, 13
18. Option 2: Pipeline Views How do you dispatch? Pub/Sub Uses subscription helpers to perform or skip different operations In this case, process_form will only be run if our request is a PUT or POST Wednesday, June 26, 13
19. Option 2: Pipeline Views Advantages: * Explicit (better than implicit) * Insert logic anywhere into request / response cycle * Very easy to debug, inspect args/kwargs/context between each method * Encourages modular design Disadvantages: * Verbose. Must specify entire pipeline if changing anything from parent * Subscription based dispatching can be complex and confusing * Not really sure if I like it yet Wednesday, June 26, 13
20. Option 2: Pipeline Views Prototype Pipeline Views Available At: https://github.com/akoumjian/django-conduit Very Helpful Site for Generic Views (good luck) http://ccbv.co.uk/ Thanks! Wednesday, June 26, 13