Django ManyToManyField Foreign Key Design - django

Question

As part of an Address Book application, I have the following in my models.py
from django.db import models
class Contact(models.Model):
contact_id= models.AutoField(auto_created=True, primary_key=True, default=1, verbose_name='ID')
name = models.CharField(max_length=100, unique=True)
contact_no = models.ManyToManyField(ContactNumberTypeField,
through='ContactContactNumber', through_fields=('contact_name','contact_type'))
def __str__(self):
return self.name
class ContactNumberTypeField(models.Model):
contact_number_type=models.AutoField(auto_created=True, primary_key=True, default=1, verbose_name='ID')
name = models.CharField(max_length=20)
contact_no = models.ManyToManyField(Contact,
through='ContactContactNumber', through_fields=('contact_name','contact_type'))
def __str__(self):
return self.name
class ContactContactNumber(models.Model):
contact_name=models.ForeignKey(Contact)
contact_type=models.ForeignKey(ContactNumberTypeField)
contact_number = models.CharField(max_length=50)
def __str__(self):
return contact_number
My question is that why is it when I run makemigrations, it throws a ContactNumberTypeField is not defined error?
Update
Correct code is as follows
from django.db import models
class Contact(models.Model):
contact_id= models.ManyToManyField('ContactNumberTypeField',
through='ContactContactNumber', through_fields=('contact_name','contact_type'))
name = models.CharField(max_length=100, unique=True)
def __str__(self):
return self.name
class ContactNumberTypeField(models.Model):
contact_number_type=models.ManyToManyField('Contact',
through='ContactContactNumber', through_fields=('contact_type','contact_name'))
name = models.CharField(max_length=20)
contact_no = models.IntegerField(max_length=20)
def __str__(self):
return self.name
class ContactContactNumber(models.Model):
contact_name=models.ForeignKey(Contact)
contact_type=models.ForeignKey(ContactNumberTypeField)
contact_number = models.CharField(max_length=50)
def __str__(self):
return contact_number

Answer 1

ContactNumberTypeField is not defined at the time of defining of Contact class. Change contact_no field to this:
class Contact(models.Model):
...
contact_no = models.ManyToManyField('ContactNumberTypeField',
through='ContactContactNumber',
through_fields=('contact_name','contact_type'))
Note the quotes around 'ContactNumberTypeField'.
The other error here is the wrong order of field names in through_fields attribute of the ContactNumberTypeField.contact_no field. It should be:
class ContactNumberTypeField(models.Model):
...
contact_no = models.ManyToManyField(Contact,
through='ContactContactNumber',
through_fields=('contact_type','contact_name'))
Read the documentation about field1 and field2.