#28316: ModelChoiceField with to_field_name fails to render a widget properly
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Reporter: László Károlyi | Owner: nobody
Type: Bug | Status: new
Component: Forms | Version: master
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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Hey guys,
I have two models something along the following:
{{{#!python
class M1(Model):
code = CharField()
name = CharField()
class M2(Model):
m1 = ForeignKey(to=M1)
}}}
I have a custom modelform, something along:
{{{#!python
class MyForm(ModelForm):
m1 = ModelChoiceField(to_field_name='code')
class Meta(object):
model = M2
exclude = ()
}}}
When I try to render this form with an instance of `M2`, because of
`to_field_name` not being `pk` of `m1`, the form will render without the
option pointing to `M1` selected.
I managed to track the problem back to `BoundField.value()`, which calls
`self.field.prepare_value(data)` with the `PK` passed to the instance of
the `ModelChoiceField`. There, `ModelChoiceField.prepare_value()` should
be able to know how to resolve the passed `PK` to the parameter in
`to_field_name`, but it doesn't do it.
Because of that, I'm forced not to pass the `to_field_name` parameter, and
let the select widget render itself with `PK`s instead of the wished
`code` fields.
Please look into this, should be fairly easy to reproduce. As I could see
from googling, [https://stackoverflow.com/questions/9827057/django-
modelchoicefield-use-something-other-than-id#comment21720211_11522820 this
has formerly already been a problem], and now it's present again.
--
Ticket URL: <https://code.djangoproject.com/ticket/28316>
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