How assigned TypedChoiceField as form class to model Field with choices?

Question

I had CharField with choices in the model, but I need for this field render as CheckboxSelectMultiple, which returns list to a form class. With TypedChoiceField form class, which automatic assigned to Field with choices, it's not validate. I decided to change form_class in the field and written a new field with TypedMultipleChoiceField form_class, to validate list.

class MultipleTypedChoiceModelField(models.Field):
    def get_internal_type(self):
        return 'MultipleTypedChoiceModelField'

    def formfield(self, **kwargs):
        defaults =  {'form_class': TypedMultipleChoiceField, }
        defaults.update(kwargs)
        return super(MultipleTypedChoiceModelField, self).formfield(**defaults)

But it is have no effect. If I commented out the choices in the model field, the type is MultipleTypedChoiceModelField. So I believe that the form_class is appointed in appliance with a list of choices definition.

def formfield(self, **kwargs):
    if self._choices: # or self.choices:
        defaults =  {'form_class': TypedMultipleChoiceField, }
        defaults.update(kwargs)
    return super(MultipleTypedChoiceModelField, self).formfield(**defaults)

But it is have no effect too. I have not found where is the assignment of form_class. Maybe I have better way to change this behavior? Adding an extra model with many to many relation I do not plan, because it is obviously unnecessary.

Answer 1

Part of the problem is that if you have something like this in your model:

myfield = models.CharField(max_length=100, choices=MY_FIELD_CHOICES)

Django is going to assume that myfield holds just one choice, nut multiple choices.

Easiest way to implement this is to just have something like this in your model:

myfield = models.CharField(max_length=100)

and then in your custom form:

myfield = forms.MultipleChoiceField(choices=MY_FIELD_CHOICES, widget=forms.CheckboxSelectMultiple())