Make fixing ModelForms easier

[Edward Sitarski]

It's not DRY to have to explicitly handle ForeignKeys and ManyToMany in ModelForms with SafeModelChoiceField and SafeModelManyToManyField:

class PostMethodForm(ModelForm):
    class Meta:
        model = Comment
        field_classes = {
            'post': SafeModelChoiceField,
        }

This is especially painful when you have lots of embedded ForeignKeys and ManyToMany fields. A somewhat DRYer solution is below:

class PostMethodForm(ModelForm):
    class Meta:
        model = Comment
        field_classes = update_safe_field_classes( model )

The function that does this is below. It allows for merging with an existing field_classes dict. It seems that an even more automatic solution is possible.

Can anyone see a problem with this approach?

from django_scopes.forms import SafeModelChoiceField, SafeModelMultipleChoiceField
from django.db.models.fields.related import ManyToManyField, ForeignKey, OneToOneField

def update_safe_field_classes( model_class, existing_field_classes = None ):
    fields = {}
    for f in model_class._meta.get_fields():
        if isinstance( f, ForeignKey ):
            fields[f.name] = SafeModelChoiceField
        elif isinstance( f, ManyToManyField ):
            fields[f.name] = SafeModelMultipleChoiceField
        elif isinstance( f, OneToOneField ):
            fields[f.name] = SafeModelChoiceField
    if existing_field_classes:
        fields.update( existing_field_classes )
    return fields

[Raphael Michel]

On first sight, I don't see an immediate problem here, could be a very useful utility

[Tobias Kunze]

Seems like something that would be useful as a decorator, because we already know that we want to use it on field_classes.