How to code a superclass field that accepts multiple subclasses? - odoo

Question

I want to have a superclass that will be inherited by subclasses.
Let's say I want the superclass mother to be inherited by child.a and child.b.
So I make these classes
mother:
class mother(osv.osv):
_name = "mother"
mother()
child.a:
class child_a(osv.osv):
_name = "child.a"
_inherit = "mother"
child_a()
child.b:
class child_b(osv.osv):
_name = "child.b"
_inherit = "mother"
child_b()
now let's say I have a class a that have a many2one connection to mother
class a(osv.osv):
_name = "a"
_columns = {
'mother' : fields.many2one('mother', 'Mother'),
}
a()
Does mother field accept both class child.a and child.b. If yes how to code the create and write methods. If not how do I achieve this in any other way? (field accepting multiple subclasses)

Answer 1

No, a many2one referencing mother can't address records of class.aor class.b.
The inheritance method used for class.a and class.b actually copies the mother features. They create two new independent tables, copy of mother, containing independent data sets.
This means that the classes are not interchangeable in any way.
Records in child.a are not present in motherand vice-versa.
What you describe can be achieved with delegation inheritance - you can think that as class.x having a mother class "embedded" in it, through a special many2one relation.
This way, when you create a new class.x record, a new mother record is also implicitly created.
But this works one way: creating a new mother record does not create a class.x record.
An example of delegation inheritance in the core modules is res.users: a User "embeds" a Partner. When a new user is created, a new Partner is also created for it.
Many2one relations to Partners will also be able to reference the User embedded Partners. But many2one relations to Users will not be able to reference Partners that are not Users.