Find object in child class from object in parent class in django

Question

Let\'s say I have a parent class (ThingsThatMigrate) and two children (Coconut and Swallow). Now let\'s say I have a ThingsThatMigrate object. How can I determine if it is

Answer 1

On a Django CMS I work with (Merengue http://www.merengueproject.org/), we store the "classname" attribute that stores what is the real class of the object.

In order to get the real instance we used the following method:

    def get_real_instance(self):
        """ get object child instance """
        def get_subclasses(cls):
            subclasses = cls.__subclasses__()
            result = []
            for subclass in subclasses:
                if not subclass._meta.abstract:
                    result.append(subclass)
                else:
                    result += get_subclasses(subclass)
            return result

        if hasattr(self, '_real_instance'):  # try looking in our cache
            return self._real_instance
        subclasses = get_subclasses(self.__class__)
        if not subclasses:  # already real_instance
            self._real_instance = getattr(self, self.class_name, self)
            return self._real_instance
        else:
            subclasses_names = [cls.__name__.lower() for cls in subclasses]
            for subcls_name in subclasses_names:
                if hasattr(self, subcls_name):
                    return getattr(self, subcls_name, self).get_real_instance()
            return self

The important thing of this function is that it keeps in mind if the class is abstract or not, wich change the logic a little bit.