Form signals idea

django_forms_forms.py

from . import signals
# ...
class BaseForm:
    # ...
    def _clean_form(self):
        try:
            signals.pre_clean.dispatch(sender=self.__class__, form=self)
            cleaned_data = self.clean()
            signals.post_clean.dispatch(sender=self.__class__, form=self, cleaned_data)
        except ValidationError as e:
            self.add_error(None, e)

django_forms_models.py

class BaseModelForm(BaseForm):
  # ...
  def save(self, commit=True):
    """
    Save this form's self.instance object if commit=True. Otherwise, add
    a save_m2m() method to the form which can be called after the instance
    is saved manually at a later time. Return the model instance.
    """
    if self.errors:
        raise ValueError(
            "The %s could not be %s because the data didn't validate." % (
                self.instance._meta.object_name,
                'created' if self.instance._state.adding else 'changed',
            )
        )
    signals.pre_save.dispatch(sender=self.__class__, form=self, commit=commit)
    if commit:
        # If committing, save the instance and the m2m data immediately.
        self.instance.save()
        self._save_m2m()
    else:
        # If not committing, add a method to the form to allow deferred
        # saving of m2m data.
        self.save_m2m = self._save_m2m
    signals.post_save.dispatch(sender=self.__class__, form=self)
    return self.instance

profile_forms.py

from .models import Profile


class ProfileForm(forms.ModelForm):
    class Meta:
        model = Profile
        exclude = ['user']
        

profile_models.py

from django.db import models


class Profile(models.Model):
    user = models.OneToOneField('auth.User')
    age = models.PositiveSmallIntegerField()
    nickname = models.CharField()

profile_receivers.py

from django.forms import signals as form_signals
from django.dispatch import receiver


@receiver(form_signals.pre_init, sender=SignUpForm)
def foo(sender, args, kwargs, **extra_kwargs):
    pass


@receiver(form_signals.post_init, sender=SignUpForm)
def add_profile_fields_to_sign_up_form(sender, form, **kwargs):
    # Add profile form fields to SignUpForm
    profile_form = ProfileForm(data=kwargs.get('data'))
    for field_name, field in profile_form.fields.items():
        form.fields[field_name] = field


@receiver(form_signals.pre_clean, sender=SignUpForm)
def baz(sender, form, **kwargs):
    pass


@receiver(form_signals.post_clean, sender=SignUpForm)
def validate_profile_fields(sender, form, cleaned_data, **kwargs):
    # Check that the nickname is not the same as the username
    if cleaned_data.get('username') == cleaned_data.get('nickname'):
        form.add_error('nickname', 'Your nickname cannot be the same as your username.')


@receiver(form_signals.pre_save, sender=SignUpForm)
def baz(sender, form, commit, **kwargs):
    pass
  

signup_forms.py

from django import forms
from django.contrib.auth.models import User

class SignUpForm(forms.ModelForm):
    class Meta:
        model = User