Question

I have a couple models using Multi-table Inheritance. like so.

class Group(models.Model):  
    title =  models.CharField(unique=True,max_length=255)


class UserGroup(Group):  
   user = models.ForeignKey(User)  
   def save(self, *args, **kwargs):  
       self.title = self.user.username  
       return super(Group, self).save(*args, **kwargs)  

UserGroups need to have unique titles and so do Groups. But It doesn’t matter if an UserGroup has the same title as a Group. Matter a fact this should happen in some cases. How can I do this?

Edit:
What if I used the save method to create an namespace.

class UserGroup(Group):  
   user = models.ForeignKey(User)  
   def save(self, *args, **kwargs):  
       self.title = "user:" + self.user.username  
       return super(UserGroup, self).save(*args, **kwargs) 

class Group(models.Model):  
    title =  models.CharField(unique=True,max_length=255)
    def save(self, *args, **kwargs):  
       self.title = "group:" + self.title
       return super(Group, self).save(*args, **kwargs)  

Would this be a good solution?

Answer 1

What you need is for Group.title and UserGroup.title to be in independent tables. The problem with your design is that in Django multi-table inheritance, child tables are never independent of their parent tables; you will need to make both Group and UserGroup inherit from another model, either concrete or abstract, and then have both children declare a title field.