Ticket #4027: 4027-model-copy.diff

db/models/base.py

@@ -14 +14 @@
 from django.utils.functional import curry
 from django.conf import settings
 from itertools import izip
+from copy import copy as copy_object
 import types
 import sys
 import os
@@ -315 +316 @@
 
     delete.alters_data = True
 
+    def copy(self):
+        """
+        Returns an already saved copy of this model instance
+        """
+        # create a copy of the current object
+        copied_self = copy_object(self)
+        # reset the id, save the new object
+        copied_self.id = None
+        copied_self.save()
+
+        # now, we need to copy all many_to_many related objects
+        for original, copy in zip(self._meta.many_to_many, copied_self._meta.many_to_many):
+            # get the managers of the fields
+            source = getattr(self, original.attname)
+            destination = getattr(copied_self, copy.attname)
+            # copy m2m field contents
+            for element in source.all():
+                destination.add(element)
+
+        # save for a second time (to apply the copied many to many fields)
+        copied_self.save()
+        return copied_self
+
     def _get_FIELD_display(self, field):
         value = getattr(self, field.attname)
         return dict(field.choices).get(value, value)