Re: Form helper functions Django

[Schalk Neethling]

Hey All,

I have looked at some of the code in our Socorro base and did some
reading online but I cannot seem to find a useful resource for this so I
thought I would ask on the list.

In forms.py there are now two places that uses this exact code:

http://sneethling.pastebin.mozilla.org/5529334

This smells of refactoring into a reusable bit but, is there a specific
way this is handled/done in Django?

Thanks!

--
Kind Regards
Schalk Neethling
Lead Front-End Engineer
Mozilla

[Paul McLanahan]

Hi Schalk,

Probably best thing is to put those methods in a mixin class and add
them to the inheritance of your form classes. You could also make a Form
subclass (e.g. DateRangeForm) that adds those methods, then inherit from
that, but I've not gone through the Form metaclass craziness to verify
if that would work without side-effect.

I'm pretty sure either strategy would work though, and it should be easy
to test.

HTH,

pmac

[Jannis Leidel]

The best way to make something like this reusable is to put it in a custom form field class. Django documentation is rather sparse about that, sadly: https://docs.djangoproject.com/en/dev/ref/forms/fields/#creating-custom-fields

All you’d have to do is to subclass the DateTimeField class and override the to_python method in the field (make sure to get the original value with a super() call).

Here’s what the current DateTimeField does: https://github.com/django/django/blob/1a2939bc26b7077e3196cea9bce52826ec7a6d9d/django/forms/fields.py#L455-L491

Since you want to check for a value of one field in the clean method of another I could also see this being applied to a subclass of a SplitDateTimeField, a special form field that consists of multiple form inputs (“MultiValueField”). In that case all you’d have to do is to implement the compress method and handle the values passed as a list the way you do in your example.

Here’s the source code of the current validation steps: https://github.com/django/django/blob/1a2939bc26b7077e3196cea9bce52826ec7a6d9d/django/forms/fields.py#L1081-L1114

Cheers,
Jannis

On 07.07.2014, at 16:25, Schalk Neethling <sneet...@mozilla.com> wrote:

> Hey All,
>
> I have looked at some of the code in our Socorro base and did some reading online but I cannot seem to find a useful resource for this so I thought I would ask on the list.
>
> In forms.py there are now two places that uses this exact code:
>
> http://sneethling.pastebin.mozilla.org/5529334
>
> This smells of refactoring into a reusable bit but, is there a specific way this is handled/done in Django?
>
> Thanks!
>

> --
> Kind Regards
> Schalk Neethling
> Lead Front-End Engineer
> Mozilla

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