#25306: Allow a limit_choices_to callable to accept the current model instance
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Reporter: Miles Hutson | Owner: nobody
Type: New feature | Status: new
Component: Forms | Version: dev
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Simon Charette):
I thought I'd bring it the following since
[https://discord.com/channels/856567261900832808/1205482292580192367/1208377208780095558
this was discussed on the Discord].
About 15 years ago [https://github.com/charettes/django-dynamic-choices I
created a now defunct third-party library that did exactly what is being
asked for here], a way to have a callable receive the model instance to
perform filtering against the available choices which confirms that this
is technically doable.
The interface was analogous to something like
{{{#!python
class Player(models.Model):
name = models.CharField()
team = models.ForeignKey('Team', limit_choices_to='allowed_teams')
def allowed_teams(self, queryset):
if self.captain_for:
return queryset.filter(pk=self.captain_for.pk)
return queryset
class Team(models.Model):
name = models.CharField()
captain = models.OneToOneField(Player, related_name='captain_for')
}}}
That would generate the equivalent of
{{{#!python
class PlayerForm(ModelForm):
class Meta:
model = Player
fields = '__all__'
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
if self.instance.pk and self.instance.captain_of:
team_field = self.fields['team']
team_field.queryset = team_field.queryset.filter(
pk=self.instance.captain_of
)
}}}
But without the boilerplate.
The library supported this feature but also a myriad of others that
allowed for example to support the common country / state selection
problem by hooking up views that would call into the backend to
dynamically select fields.
All to say that there might already be existing third packages
implementing this feature if someone wants to tinker on how it can be
done.
--
Ticket URL: <https://code.djangoproject.com/ticket/25306#comment:7>
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