Migrate the randomize module to the new storage model

common/lib/xmodule/xmodule/randomize_module.py

@@ -36,29 +36,25 @@ class RandomizeModule(XModule):
         modules.
 """
 
-    def __init__(self, system, location, definition, descriptor,
-                 instance_state=None, shared_state=None, **kwargs):
-        XModule.__init__(self, system, location, definition, descriptor,
-                         instance_state, shared_state, **kwargs)
+    choice = Integer(help="Which random child was chosen", scope=Scope.student_state)
+
+    def __init__(self, *args, **kwargs):
+        XModule.__init__(self, *args, **kwargs)
 
         # NOTE: calling self.get_children() creates a circular reference--
         # it calls get_child_descriptors() internally, but that doesn't work until
         # we've picked a choice
         num_choices = len(self.descriptor.get_children())
 
-        self.choice = None
-        if instance_state is not None:
-            state = json.loads(instance_state)
-            self.choice = state.get('choice', None)
-            if self.choice > num_choices:
-                # Oops.  Children changed. Reset.
-                self.choice = None
+        if self.choice > num_choices:
+            # Oops.  Children changed. Reset.
+            self.choice = None
 
         if self.choice is None:
             # choose one based on the system seed, or randomly if that's not available
             if num_choices > 0:
-                if system.seed is not None:
-                    self.choice = system.seed % num_choices
+                if self.system.seed is not None:
+                    self.choice = self.system.seed % num_choices
                 else:
                     self.choice = random.randrange(0, num_choices)
 
@@ -73,10 +69,6 @@ class RandomizeModule(XModule):
             self.child = None
 
 
-    def get_instance_state(self):
-        return json.dumps({'choice': self.choice})
-
-
     def get_child_descriptors(self):
         """
         For grading--return just the chosen child.