40 lines
1.9 KiB
Markdown
40 lines
1.9 KiB
Markdown
---
|
||
layout: post
|
||
title: "@ParamConverter à la Django"
|
||
date: 2015-06-07 18:14:32
|
||
tags: [python, django]
|
||
published: true
|
||
author:
|
||
name: Gergely Polonkai
|
||
email: gergely@polonkai.eu
|
||
---
|
||
One thing I really miss from [Django](https://www.djangoproject.com/)
|
||
is [Symfony](http://symfony.com)’s
|
||
[@ParamConverter](http://symfony.com/doc/current/bundles/SensioFrameworkExtraBundle/annotations/converters.html). It
|
||
made my life so much easier while developing with Symfony. In Django,
|
||
of course, there is
|
||
[get_object_or_404](https://docs.djangoproject.com/en/dev/topics/http/shortcuts/#get-object-or-404),
|
||
but, for example, in one of my projects I had a view that had to resolve 6(!)
|
||
objects from the URL, and writing `get_object_or_404` six times is not what a
|
||
programmer likes to do (yes, this view had a refactor later on). A quick Google
|
||
search gave me one [usable
|
||
result](http://openclassrooms.com/forum/sujet/middleware-django-genre-paramconverter-doctrine)
|
||
(in French), but it was very generalized that I cannot always use. Also, it was
|
||
using a middleware, which may introduce performance issues
|
||
sometimes<sup>[citation needed]</sup>. So I decided to go with decorators, and
|
||
at the end, I came up with this:
|
||
|
||
{% gist 498a32297f39b4960ad7 helper.py %}
|
||
|
||
Now I can decorate my views, either class or function based, with
|
||
`@convert_params(User, (Article, 'aid'), (Paragraph, None, 'pid'),
|
||
(AnotherObject, None, None, 'obj'))` and all the magic happens in the
|
||
background. The `user_id` parameter passed to my function will be
|
||
popped off, and be resolved against the `User` model by using the `id`
|
||
field; the result is put in the new `user` parameter. For Article, the
|
||
`aid` parameter will be matched against the `id` field of the
|
||
`Article` model putting the result into `article`, and finally, the
|
||
`another_object_id` will be matched against the `id` field of the
|
||
`AnotherObject` model, but in this case, the result is passed to the
|
||
original function as `obj`.
|