ChoiceFilter callable choices

[teelee7133]

Hello,

For ChoiceFilter (and other related ones), is it possible, or will it make sense, to have the 'choices' callable to behave like the ChoiceField in django, where 'it is evaluated each time the field’s form is initialized'?

https://docs.djangoproject.com/en/1.11/ref/forms/fields/#choicefield

(I am happy to draft a PR if this sounds a reasonable feature request)

Thanks!

[carltongibson]

... or will it make sense...

That's the question isn't is? 🙂

Can you explain your use-case a bit so we can see? Thanks!

[teelee7133]

Indeed! 🙂

I think currently in ChoiceFilter, choices parameter accepts a callable. But if datetime function or ORM functions are used within that callable, then, ideally, it would be best the choices data to be materialized when the FilterSet instance is created, instead of when the FilterSet class is created.

Some naive example:
Consider some reporting system with the following models (I have not tested the syntax):

class AccountTransactionType(models.Model):
    name = models.CharField(max_length=100)

class AccountTransaction(models.Model):
    transaction_type=models.ForeighKey(AccountTransactionType)
    transaction_date=models.DateTimeField()
    #....

# ------------
def recent_type_choice_fn():
    # Lets get some more recent account type
    return AccountTransaction.objects.filter(
        transaction_date__gt=(timezone.now() - timezone.delta(days=30))
    ).values_list('transaction_type', 'transaction_type__name')

class AccountingTransactionFilter(django_filter.FilterSet):
    transaction_type = ChoiceFilter(
        choices=recent_type_choice_fn, 
        #....
    )
   

Here we want to show transaction type with recent entries e.g. last 30 days, in the filter. However, choices for AccountingTransactionFilter will be fixed when the class is created. If we leave django server running for a month, the choices won't change. In order to have refreshed choices, either ChoiceFilter have to be subclassed, or restart django server...

Let me know of your thoughts, thanks!

[rpkilby]

Yep. The problem is choice resolution during the field instantiation. Could you try installing the branch from #680? I believe that this incidentally fixes the issue you're describing here.

[rpkilby]

It might not also be a bad idea for me to add a test in 680 ensuring that choices are resolved during FilterSet form creation instead of during filter instantiation.

[teelee7133]

Yep rpkilby, I gave PR #680 a quick test, and it looks like the PR solves the issue. 👍 Thanks for the PR!

When will it likely be released? 🙂

[carltongibson]

When will it likely be released? 🙂

It'll be a week or two (at least). I need to finish 1.0.3 and then look at the proposals for 1.1 (which includes this one.) If you need it before then I'd suggest installing from the branch

[teelee7133]

version 1.1 sounds good, thanks!