Refactor callback subscription stuff to a mixin

lib/tfw/components/history_monitor.py

@@ -2,6 +2,8 @@ from watchdog.observers import Observer
 from watchdog.events import PatternMatchingEventHandler
 from os.path import dirname
 
+from tfw.components.mixins.callback_mixin import CallbackMixin
+
 
 class CallbackEventHandler(PatternMatchingEventHandler):
     def __init__(self, files, *callbacks):
@@ -13,12 +15,12 @@ class CallbackEventHandler(PatternMatchingEventHandler):
             callback()
 
 
-class HistoryMonitor:
+class HistoryMonitor(CallbackMixin):
     def __init__(self, histfile):
+        CallbackMixin.__init__(self)
         self.histfile = histfile
         self._history = []
         self._last_length = len(self._history)
-        self._callbacks = []
         self.observer = Observer()
         self.observer.schedule(CallbackEventHandler([self.histfile],
                                                     self._fetch_history,
@@ -29,10 +31,6 @@ class HistoryMonitor:
     def history(self):
         return self._history
 
-    @property
-    def callbacks(self):
-        return self._callbacks
-
     def _fetch_history(self):
         self._last_length = len(self._history)
         with open(self.histfile, 'r') as ifile:
@@ -40,8 +38,7 @@ class HistoryMonitor:
 
     def _invoke_callbacks(self):
         if self._last_length < len(self._history):
-            for callback in self.callbacks:
-                callback(self.history)
+            self._execute_callbacks(self.history)
 
     def watch(self):
         self.observer.start()

lib/tfw/components/mixins/callback_mixin.py

@@ -0,0 +1,17 @@
+from functools import partial
+
+
+class CallbackMixin:
+    def __init__(self):
+        self._callbacks = []
+
+    def subscribe_callback(self, callback, *args, **kwargs):
+        fun = partial(callback, *args, **kwargs)
+        self._callbacks.append(fun)
+
+    def unsubscribe_callback(self, callback):
+        self._callbacks.remove(callback)
+
+    def _execute_callbacks(self, *args, **kwargs):
+        for callback in self._callbacks:
+            callback(*args, **kwargs)