Merge pull request #195 from jazzband/updated_signal

Added the old value to the config_updated signal

constance/backends/database/__init__.py

@@ -77,6 +77,7 @@ class DatabaseBackend(Backend):
         return value
 
     def set(self, key, value):
+        old_value = self.get(key)
         constance, created = self._model._default_manager.get_or_create(
             key=self.add_prefix(key), defaults={'value': value}
         )
@@ -87,7 +88,7 @@ class DatabaseBackend(Backend):
             self._cache.set(key, value)
 
         signals.config_updated.send(
-            sender=config, updated_key=key, new_value=value
+            sender=config, key=key, old_value=old_value, new_value=value
         )
 
     def clear(self, sender, instance, created, **kwargs):

constance/backends/redisd.py

@@ -48,7 +48,8 @@ class RedisBackend(Backend):
                 yield key, loads(value)
 
     def set(self, key, value):
+        old_value = self.get(key)
         self._rd.set(self.add_prefix(key), dumps(value))
         signals.config_updated.send(
-            sender=config, updated_key=key, new_value=value
+            sender=config, key=key, old_value=old_value, new_value=value
         )

constance/signals.py

@@ -1,5 +1,5 @@
 import django.dispatch
 
 config_updated = django.dispatch.Signal(
-    providing_args=['updated_key', 'new_value']
+    providing_args=['key', 'old_value', 'new_value']
 )

docs/index.rst

@@ -81,8 +81,8 @@ You can use it as:
     from constance.signals import config_updated
 
     @receiver(config_updated)
-    def constance_updated(sender, updated_key, new_value, **kwargs):
-        print(sender, updated_key, new_value)
+    def constance_updated(sender, key, old_value, new_value, **kwargs):
+        print(sender, key, old_value, new_value)
 
 The sender is the ``config`` object, and the ``updated_key`` and ``new_value``
 are the ones just changed.