  
  ModelForms and custom fields
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  If you use :class:`~django.db.models.SubfieldBase`, :meth:`to_python`
  will be called every time an instance of the field is assigned a
  value. This means that whenever a value may be assigned to the field,
  you need to ensure that it will be of the correct datatype, or that
  you handle any exceptions.
  
 
</s> remove This ensures that the :meth:`to_python` method, documented below, will always be
called when the attribute is initialized.
 </s> add This ensures that the :meth:`.to_python` method, documented below, will always
be called when the attribute is initialized. </s> remove custom form field, and/or implementing the :meth:`formfield` method on
 </s> add custom form field, and/or implementing the :meth:`.formfield` method on </s> remove and pass the rest to the :meth:`get_db_prep_lookup` method of the parent class.
 </s> add and pass the rest to the :meth:`.get_db_prep_lookup` method of the parent class. </s> remove This is the reverse of :meth:`to_python` when working with the
 </s> add This is the reverse of :meth:`.to_python` when working with the </s> remove :meth:`get_db_prep_value` is the method where those conversions should
 </s> add :meth:`.get_db_prep_value` is the method where those conversions should
If you use :class:`~django.db.models.SubfieldBase`, :meth:`.to_python`
  
  ModelForms and custom fields
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
If you use :class:`~django.db.models.SubfieldBase`, :meth:`.to_python`
  will be called every time an instance of the field is assigned a
  value. This means that whenever a value may be assigned to the field,
  you need to ensure that it will be of the correct datatype, or that
  you handle any exceptions.
  
keep keep keep keep replace keep keep keep keep keep
 Fixed #15308 -- Sphinx/reST fixes for the Custom Model Fields docs.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15547 bcc190cf-cafb-0310-a4f2-bffc1f526a37 
docs/howto/custom-model-fields.txt