#28210: `<orm_object>._state.adding` behaviour and model inheritance
--------------------------------+--------------------------------------
Reporter: Ivaylo Donchev | Owner: nobody
Type: Uncategorized | Status: new
Component: Uncategorized | Version: 1.11
Severity: Normal | Resolution:
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Ivaylo Donchev):
Yeah, but it's not about the **_state.db**.Basically, if we have these
two models:
{{{
class Parent(models.Model):
pass
class ChildA(Parent):
pass
class ChildB(Parent):
pass
}}}
and we create "ChildA" object with **obj = ChildA.objects.create()**,
we'll have 2 new instances - ***(ChildA) obj*** and ***(Parent)
obj.parent_ptr)***. Now, if you try to create "ChildB" instance as
follows:
{{{
parent = obj.parent_ptr # parent._state.adding == True
child_b = ChildB(parent_ptr=obj.parent_ptr)
child_b.__dict__.update(parent) # to set all required attributes (if
any)
child_b.full_clean() # this will throw an error for all of the unique
fields of the parent instance ("id"for example)
child_b.save()
}}}
So, if you set {{{ obj.parent_ptr._state.adding = False }}} as soon as obj
is created, the code above is working without errors.
Basically, the problem is that if we don't modify the _state's adding,
it's no possible to create a new instance with the same parent_ptr.
--
Ticket URL: <https://code.djangoproject.com/ticket/28210#comment:2>
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