Refactor Singleton class

gajim/common/helpers.py

@@ -1520,3 +1520,11 @@ def save_roster_position(window):
     log.debug('Save roster position: %s %s', x_pos, y_pos)
     app.config.set('roster_x-position', x_pos)
     app.config.set('roster_y-position', y_pos)
+
+
+class Singleton(type):
+    _instances = {}
+    def __call__(cls, *args, **kwargs):
+        if cls not in cls._instances:
+            cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
+        return cls._instances[cls]

gajim/plugins/helpers.py

@@ -21,7 +21,7 @@ Helper code related to plug-ins management system.
 :license: GPL
 '''
 
-__all__ = ['log', 'log_calls', 'Singleton']
+__all__ = ['log', 'log_calls']
 
 from typing import List
 
@@ -115,26 +115,6 @@ class log_calls:
 
         return wrapper
 
-class Singleton(type):
-    '''
-    Singleton metaclass.
-    '''
-    def __init__(cls, name, bases, dic):
-        super(Singleton, cls).__init__(name, bases, dic)
-        cls.instance = None
-
-    def __call__(cls, *args, **kwargs):
-        if cls.instance is None:
-            cls.instance = super(Singleton, cls).__call__(*args, **kwargs)
-            #log.debug('%(classname)s - new instance created'%{
-                #'classname' : cls.__name__})
-        else:
-            pass
-            #log.debug('%(classname)s - returning already existing instance'%{
-                #'classname' : cls.__name__})
-
-        return cls.instance
-
 
 def get_builder(file_name: str, widgets: List[str] = None) -> Builder:
     return Builder(file_name,

gajim/plugins/pluginmanager.py

@@ -38,9 +38,10 @@ from gajim.common import configpaths
 from gajim.common import modules
 from gajim.common.i18n import _
 from gajim.common.exceptions import PluginsystemError
+from gajim.common.helpers import Singleton
 from gajim.plugins import plugins_i18n
 
-from gajim.plugins.helpers import log, log_calls, Singleton
+from gajim.plugins.helpers import log, log_calls
 from gajim.plugins.helpers import GajimPluginActivateException
 from gajim.plugins.gajimplugin import GajimPlugin, GajimPluginException
 
@@ -73,8 +74,6 @@ class PluginManager(metaclass=Singleton):
                'destructors' (classes that register GUI extension points)
     '''
 
-    __metaclass__ = Singleton
-
     #@log_calls('PluginManager')
     def __init__(self):
         self.plugins = []