#23549: Model form's model_to_dict using value_from_object instead of to_python
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Reporter: mwaterfall | Owner: nobody
Type: Bug | Status: new
Component: Forms | Version: 1.7
Severity: Normal | Keywords: form, modelform, field
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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Background: I'm using a [https://github.com/bradjasper/django-jsonfield/
JSONField] model field to store a list of strings in a field, and I'm
trying to create a model form with a series of checkboxes that allows me
to multiple select zero or more of these string options using
`TypedMultipleChoiceField` and `CheckboxSelectMultiple`.
Issue: When the form is rendered, the checkboxes that should be checked
aren't checked. When saving the form, the checked values are correctly
saved and serialised by the field.
Cause:
The reason the checkboxes aren't getting checked is down to the function
`model_to_dict`, that converts a model instance to a dict ready to
populate a ModelForm. The value is retrieved from instance fields using
`value_from_object`. Why is `to_python` not used?
The JSONField is following the guidelines to create a custom model field,
overriding the `to_python` to deserialise the raw value from the DB and
return a python object. This `model_to_dict` is bypassing this, not
allowing custom fields to deserialise values before they are used to
populate a form.
Hence the form is receiving the JSON string as opposed to the deserialised
list, and causing things to be rendered incorrectly.
Here's the line in question:
https://github.com/django/django/blob/1.7/django/forms/models.py#L151
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Ticket URL: <https://code.djangoproject.com/ticket/23549>
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