What is the best way to indicate Main/Preffered object of ones related by they ForeignKey in django? -

i got these models:

person(models.model):     first_name = models.charfield(max_lenght=10)  phone(models.model):     number = models.charfield(max_lenght=10)     person = models.foreignkey(person) 

i want indicate of phone numbers if proffered each person got:

person(models.model):     first_name = models.charfield(max_lenght=10)     main_phone = models.onetoonefield(phone)  phone(models.model):     number = models.charfield(max_lenght=10)     person = models.foreignkey(person) 

and filtering choices in form , validating them make sure person owner of main_phone

it should work buts looks little "spaghetti like". maybe have best practices share?

i made custom field encapsulates overridden-save-method pattern (as used in @eugene's answer).

https://pypi.python.org/pypi/django-exclusivebooleanfield

phone(models.model):     number = models.charfield(max_length=10)     person = models.foreignkey(person)     is_main = exclusivebooleanfield(default=false, on=('person',))