Question

I am using django-tastypie to create a rest API for my webapp.
I want to create classes like mentioned below without typing them all out explicitly(I have more than a 100 classes)

class CityResource(ModelResource):
    class Meta:
        queryset = City.objects.all()
class StateResource(ModelResource):
    class Meta:
        queryset = State.objects.all()
etc...

I was thinking of using metaclasses in python(my approach might be wrong but still want to solve it this way as I want to see how metaclass can help me and maybe a good way to learn it in a real life problem)

I tried this:

class ClassFactory(type):
    def __new__(cls, name, bases, dct):
        return type.__new__(cls, name, bases, dct)

for model in get_models(app):
    name = "%sResource" % model._meta.object_name
    ClassFactory(name, (ModelResource, ), {'Meta':type('Meta', (), {'queryset': model.objects.all()})})

But this gives an error:

TypeError: metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases

I googled up on this and everywhere it mentions about how if a class derives from 2 other classes that have two different metaclass then the class I make must have a metaclass that was derived from the two metaclasses[*].

1. How does this error happen in my case, as I am deriving from the same class ModelResource?
2. I am not sure I understand [*]

I might be solving this problem the wrong way, but need some pointers.

Answer 1

(Reposted from comment.)

I don’t think you need the ClassFactory “metaclass” at all.

klass = type(name, (ModelResource, ), {...})

should get you a new class that’s derived from ModelResource, as you want.