You can implement this using generic relationships by manually creating the junction table between message and recipient:
from django.db import models
from django.contrib.contenttypes import generic
from django.contrib.contenttypes.models import ContentType
class Client(models.Model):
city = models.CharField(max_length=16)
# These aren't required, but they'll allow you do cool stuff
# like "person.sent_messages.all()" to get all messages sent
# by that person, and "person.received_messages.all()" to
# get all messages sent to that person.
# Well...sort of, since "received_messages.all()" will return
# a queryset of "MessageRecipient" instances.
sent_messages = generic.GenericRelation('Message',
content_type_field='sender_content_type',
object_id_field='sender_id'
)
received_messages = generic.GenericRelation('MessageRecipient',
content_type_field='recipient_content_type',
object_id_field='recipient_id'
)
class Meta:
abstract = True
class PersonClient(Client):
first_name = models.CharField(max_length=16)
last_name = models.CharField(max_length=16)
gender = models.CharField(max_length=1)
def __unicode__(self):
return u'%s %s' % (self.last_name, self.first_name)
class CompanyClient(Client):
name = models.CharField(max_length=32)
tax_no = models.PositiveIntegerField()
def __unicode__(self):
return self.name
class Message(models.Model):
sender_content_type = models.ForeignKey(ContentType)
sender_id = models.PositiveIntegerField()
sender = generic.GenericForeignKey('sender_content_type', 'sender_id')
msg_body = models.CharField(max_length=1024)
def __unicode__(self):
return u'%s...' % self.msg_body[:25]
class MessageRecipient(models.Model):
message = models.ForeignKey(Message)
recipient_content_type = models.ForeignKey(ContentType)
recipient_id = models.PositiveIntegerField()
recipient = generic.GenericForeignKey('recipient_content_type', 'recipient_id')
def __unicode__(self):
return u'%s sent to %s' % (self.message, self.recipient)
You'd use the above models like so:
>>> person1 = PersonClient.objects.create(first_name='Person', last_name='One', gender='M')
>>> person2 = PersonClient.objects.create(first_name='Person', last_name='Two', gender='F')
>>> company = CompanyClient.objects.create(name='FastCompany', tax_no='4220')
>>> company_ct = ContentType.objects.get_for_model(CompanyClient)
>>> person_ct = ContentType.objects.get_for_model(person1) # works for instances too.
# now we create a message:
>>> msg = Message.objects.create(sender_content_type=person_ct, sender_id=person1.pk, msg_body='Hey, did any of you move my cheese?')
# and send it to a coupla recipients:
>>> MessageRecipient.objects.create(message=msg, recipient_content_type=person_ct, recipient_id=person2.pk)
>>> MessageRecipient.objects.create(message=msg, recipient_content_type=company_ct, recipient_id=company.pk)
>>> MessageRecipient.objects.count()
2
As you can see, this is a far more verbose (complicated?) solution. I'd probably keep it simple and go with Prariedogg's solution above.