Clean up

rest_framework/throttling.py

@@ -188,16 +188,24 @@ class ScopedRateThrottle(SimpleRateThrottle):
     scope_attr = 'throttle_scope'
 
     def __init__(self):
+        # Override the usual SimpleRateThrottle, because we can't determine
+        # the rate until called by the view.
         pass
 
     def allow_request(self, request, view):
+        # We can only determine the scope once we're called by the view.
         self.scope = getattr(view, self.scope_attr, None)
 
+        # If a view does not have a `throttle_scope` always allow the request
         if not self.scope:
             return True
 
+        # Determine the allowed request rate as we normally would during
+        # the `__init__` call.
         self.rate = self.get_rate()
         self.num_requests, self.duration = self.parse_rate(self.rate)
+
+        # We can now proceed as normal.
         return super(ScopedRateThrottle, self).allow_request(request, view)
 
     def get_cache_key(self, request, view):
@@ -207,18 +215,12 @@ class ScopedRateThrottle(SimpleRateThrottle):
         Otherwise generate the unique cache key by concatenating the user id
         with the '.throttle_scope` property of the view.
         """
-        scope = getattr(view, self.scope_attr, None)
-
-        if not scope:
-            # Only throttle views if `.throttle_scope` is set on the view.
-            return None
-
         if request.user.is_authenticated():
             ident = request.user.id
         else:
             ident = request.META.get('REMOTE_ADDR', None)
 
         return self.cache_format % {
-            'scope': scope,
+            'scope': self.scope,
             'ident': ident
         }