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Django's multiple-choice model field with static choices
Field with multiple *static* choices (not via m2m)
Value is stored in DB as comma-separated values
Default widget is forms.CheckboxSelectMultiple
Python value: list of values
Original Django snippet:
It's 6 years old and doesn't work with latest Django
Also it implements 'max_choices' functionality - I have removed it for simplicity
from django import forms
from django.db import models
from django.core import exceptions
from django.utils.encoding import force_text
from south.modelsinspector import add_introspection_rules
class MultipleSelectFormField(forms.MultipleChoiceField):
widget = forms.CheckboxSelectMultiple
class MultipleSelectField(models.Field):
__metaclass__ = models.SubfieldBase
def get_internal_type(self):
return "CharField"
def get_choices_default(self):
return self.get_choices(include_blank=False)
def formfield(self, **kwargs):
# don't call super, as that overrides default widget if it has choices
defaults = {
'required': not self.blank,
'label': self.verbose_name.capitalize(),
'help_text': self.help_text,
'choices': self.choices
if self.has_default():
defaults['initial'] = self.get_default()
return MultipleSelectFormField(**defaults)
def get_db_prep_value(self, value, connection, prepared=False):
if isinstance(value, list):
return ",".join(map(unicode, value))
if value is None or isinstance(value, basestring):
return value
return unicode(value)
def to_python(self, value):
if value is None or isinstance(value, list):
return value
return unicode(value).split(",")
def validate(self, value, model_instance):
if not self.editable:
# Skip validation for non-editable fields.
if self._choices and value not in self.empty_values:
if not isinstance(value, list):
value = [value]
if set(dict(self.choices).keys()) & set(value) == set(value):
raise exceptions.ValidationError(
params={'value': value},
if value is None and not self.null:
raise exceptions.ValidationError(self.error_messages['null'], code='null')
if not self.blank and value in self.empty_values:
raise exceptions.ValidationError(self.error_messages['blank'], code='blank')
def contribute_to_class(self, cls, name, virtual_only=False):
super(MultipleSelectField, self).contribute_to_class(cls, name)
if self.choices:
fieldname =
choicedict = dict(self.choices)
def func(self):
value = getattr(self, fieldname)
if not isinstance(value, list):
value = [value]
return ", ".join([force_text(choicedict.get(i, i)) for i in value])
setattr(cls, 'get_%s_display' % fieldname, func)
# Provide South support
#add_introspection_rules([], ["^app_name\.fields\.MultipleSelectField"])
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