FSM for Feed

zipline/core/component.py

@@ -568,3 +568,23 @@ class Component(object):
             pid     = os.getpid()          ,
             pointer = hex(id(self))        ,
         )
+
+
+    @property
+    def state(self):
+        if not hasattr(self, '_state'):
+            self._state = self.initial_state
+        else:
+            return self._state
+
+    @state.setter
+    def state(self, new):
+        if not hasattr(self, '_state'):
+            self._state = self.initial_state
+
+        old = self._state
+
+        if (old, new) in self.workflow:
+            self._state = new
+        else:
+            raise RuntimeError("Invalid State Transition : %s -> %s" %(old, new))