#18172: Admin form fails to generate proper ModelMultipleChoiceField when using
iterable model
-------------------------------+--------------------
Reporter: eric.olstad@… | Owner: nobody
Type: Uncategorized | Status: new
Component: Forms | Version: 1.4
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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When using default admin forms for a model with a ManyToManyField to an
iterable model (defines {{{__iter__}}}), the select control generated will
have options that have list values instead of the primary key on the
model.
Example:
{{{
class MyIterableModel(models.Model):
def __iter__(self):
for item in self.items:
yield item
class MyItem(models.Model):
owner = models.ForeignKey(MyIterableModel, related_name=items)
class MyOtherModel(models.Model):
myiterables = model.ManyToManyField(MyIterableModel)
}}}
In the admin:
{{{
admin.site.register(models.MyOtherModel)
}}}
When viewing the MyOtherModel page in the admin, the control for the
ManyToManyField will have lists of primary keys as each option value.
{{{
<select multiple="multiple" name="myiterablemodels"
id="id_myiterablemodels">
<option value="[35636, 35383]">Yada Yada</option>
</select>
}}}
This of course generates "not a valid value for primary key" when
submitting.
This is because django/forms/models.py prepare_value returns a list.
{{{
1035 def prepare_value(self, value):
1036 if hasattr(value, '__iter__'):
1037 return [super(ModelMultipleChoiceField,
self).prepare_value(v) for v in value]
1038 return super(ModelMultipleChoiceField,
self).prepare_value(value)
}}}
I'm not sure why prepare_value returns a list in that case, so I don't
have suggestions for a fix. The workaround is to not use iterable models.
--
Ticket URL: <https://code.djangoproject.com/ticket/18172>
Django <https://code.djangoproject.com/>
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