> It does not work at all. For some reason, final_type also gets
> upcasted to MediaObject?!
I found the solution, now. The problem was that the __init__ method of
a Model is also called when objects are restored from the database. So
when the base class gets initialized by the QueryManager, it
overwrites final_type with the wrong value. The solution is simple:
overwrite the save method instead of __init__. Here is a complete
recipe:
class BaseClass(models.Model) :
final_type = models.ForeignKey(ContentType)
def save(self,*args) :
self.final_type =
ContentType.objects.get_for_model(type(self))
super(BaseClass,self)save(*args)
def cast(self) :
return
self.final_type.get_object_for_this_type(id=self.id)
class DerivedClass(ParentClass) :
pass
Here is an example:
obj = DerivedClass()
obj.save()
obj = get_object_or_404(BaseClass, id=3).cast()
# obj is now of type DerivedClass
Best,
- harold -
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