Allow functions as FactoryOptions.model

Facilitates the use of a factory function, that may create several
related objects at once.

docs/changelog.rst

@@ -16,6 +16,7 @@ ChangeLog
 
 - :issue:`1031`: Do not require :attr:`~factory.alchemy.SQLAlchemyOptions.sqlalchemy_session` when
   :attr:`~factory.alchemy.SQLAlchemyOptions.sqlalchemy_session_factory` is provided.
+- :issue:`1072`: Allow using functions as models for a :attr:`~factory.FactoryOptions.model`.
 
 *Removed:*
 

factory/base.py

@@ -2,6 +2,7 @@
 
 
 import collections
+import inspect
 import logging
 import warnings
 from typing import Generic, List, Type, TypeVar
@@ -243,6 +244,7 @@ def _get_counter_reference(self):
         if (self.model is not None
                 and self.base_factory is not None
                 and self.base_factory._meta.model is not None
+                and inspect.isclass(self.model)
                 and issubclass(self.model, self.base_factory._meta.model)):
             return self.base_factory._meta.counter_reference
         else:

tests/test_base.py

@@ -281,6 +281,22 @@ class Meta:
         ones = {x.one for x in (parent, alt_parent, sub, alt_sub)}
         self.assertEqual(4, len(ones))
 
+    def test_inheritance_with_function_as_meta_model(self):
+        def make_test_object(**kwargs):
+            return TestObject(**kwargs)
+
+        class TestObjectFactory(base.Factory):
+            class Meta:
+                model = make_test_object
+
+            one = "foo"
+
+        class TestSubFactory(TestObjectFactory):
+            one = "bar"
+
+        sub = TestSubFactory.build()
+        self.assertEqual(sub.one, "bar")
+
 
 class FactorySequenceTestCase(unittest.TestCase):
     def setUp(self):