Added a ModelClass.copy_model() class constructor to cover unsaved 'casting' between model types. Basically just copies over fields and relationships. Fixes scholrly#7.

Author: mhluongo

neo4django/models/base.py

@@ -150,26 +150,32 @@ def using(self):
     @classmethod
     def from_model(cls, neo_model):
         """
-        Factory method that essentially allows "casting" from model to model.
-        The newly returned model instance is validated, but unsaved.
+        Factory method that essentially allows "casting" from a saved model
+        instance to another saved model instance. These instances are both
+        represented by the same node in the graph, but allow different views
+        of the same properties and relationships.
         """
         if neo_model.node is not None:
             new_model = cls._neo4j_instance(neo_model.node)
             return new_model
         else:
-            #clone field by field
-            onto_field_names = [f.attname for f in neo_model._meta.fields]
-            new_model = cls()
-            for field in neo_model._meta.fields:
-                name = field.attname
-                if name not in onto_field_names or name in ('pk', 'id'): continue
-                val = getattr(neo_model, name)
-                if isinstance(val, models.Manager):
-                    for obj in val.all():
-                        getattr(new_model, name).add(obj)
-                else:
-                    setattr(new_model, name, val)
-            return new_model
+            raise TypeError('from_model() only operates on saved models.')
+
+
+    @classmethod
+    def copy_model(cls, neo_model):
+        onto_field_names = [f.attname for f in neo_model._meta.fields]
+        new_model = cls()
+        for field in neo_model._meta.fields:
+            name = field.attname
+            if name not in onto_field_names or name in ('pk', 'id'): continue
+            val = getattr(neo_model, name)
+            if isinstance(val, models.Manager):
+                for obj in val.all():
+                    getattr(new_model, name).add(obj)
+            else:
+                setattr(new_model, name, val)
+        return new_model
 
     @classmethod
     def index(cls, using=DEFAULT_DB_ALIAS):

neo4django/tests/tests.py

@@ -260,8 +260,8 @@ class TestSubclass(neo4django.NodeModel):
 
     assert not hasattr(n2, 'age'),  "Age should not be defined, as the new class didn't define it."
 
-def test_saved_model_casting():
-    """Tests functional model to model "casting"."""
+def test_model_casting():
+    """Tests functional saved model to model "casting"."""
     #create a model similar to person, but with relationships
     class Doppelganger(neo4django.NodeModel):
         name = neo4django.StringProperty()
@@ -285,14 +285,22 @@ class Vierfachganger(neo4django.NodeModel):
     double_imposter = Vierfachganger.from_model(imposter)
     eq_(abe, double_imposter.original)
 
+def test_model_casting_validation():
+    raise NotImplementedError('Write this test!')
+
 def test_model_copy():
-    pass
+    class NameOwner(neo4django.NodeModel):
+        name = neo4django.StringProperty()
+        confidantes = neo4django.Relationship(Person, neo4django.Outgoing.KNOWS)
 
-def test_unsaved_model_casting():
-    pass
+    pete = Person(name='Pete')
+    pete2 = NameOwner.copy_model(pete)
+    eq_(pete.name, pete2.name)
 
-def test_model_casting_validation():
-    raise NotImplementedError('Write this test!')
+    pete2.confidantes.add(pete)
+    pete3 = NameOwner.copy_model(pete2)
+    assert pete in list(pete3.confidantes.all()),\
+            "Copying isn't commuting relationships!"
 
 def test_array_property_validator():
     """Tests that ArrayProperty validates properly."""

reg_settings.py

@@ -53,7 +53,8 @@
 	'test_filter_lte',
 	'test_filter_date_range',
 	'test_model_casting',
-	'test_model_casting_validation']
+	'test_model_casting_validation',
+	'test_model_copy']
 should_fail=[
 	'test_dates',
 	'test_filter_iexact',
@@ -64,5 +65,4 @@
 	'test_str_array_property_validator',
 	'test_url_array_property_validator',
 	'test_type_query',
-	'test_model_casting',
 	'test_model_casting_validation']