jpadilla · February 17, 2013 23:01 · Feb 17, 2013
diff --git a/gistfile1.py b/gistfile1.py
@@ -0,0 +1,45 @@
+from django.forms.models import model_to_dict
+
+
+class ModelDiffMixin(object):
+    """
+    A model mixin that tracks model fields' values and provide some useful api
+    to know what fields have been changed.
+    """
+
+    def __init__(self, *args, **kwargs):
+        super(ModelDiffMixin, self).__init__(*args, **kwargs)
+        self.__initial = self._dict
+
+    @property
+    def diff(self):
+        d1 = self.__initial
+        d2 = self._dict
+        diffs = [(k, (v, d2[k])) for k, v in d1.items() if v != d2[k]]
+        return dict(diffs)
+
+    @property
+    def has_changed(self):
+        return bool(self.diff)
+
+    @property
+    def changed_fields(self):
+        return self.diff.keys()
+
+    def get_field_diff(self, field_name):
+        """
+        Returns a diff for field if it's changed and None otherwise.
+        """
+        return self.diff.get(field_name, None)
+
+    def save(self, *args, **kwargs):
+        """
+        Saves model and set initial state.
+        """
+        super(ModelDiffMixin, self).save(*args, **kwargs)
+        self.__initial = self._dict
+
+    @property
+    def _dict(self):
+        return model_to_dict(self, fields=[field.name for field in
+                             self._meta.fields])