Hello all: I'm a new Zope developer and I a bit confused with the Plugins Model... I have created a Plugin container and a Plugin. All works ok, but when I try to view the Plugin Container management interface Zope return me an error. The teory is (Summarized): MyPluginContainer extends PlugInContainer and adds something like this: class foo(PlugInContainer): """Foo foo""" meta_type = 'foo' __implements__= Prueba Confs = PlugInGroup('Configuraciones', ['Configuraciones'], attr='listaPlugins') __plugin_groups__ = (Confs) def __init__(self, id) self.id = id self.listaPlugins = [] ... ########################################################### The plugin is like this: class miPlugin(PlugIn): """ miplugin """ meta_type = 'miPlugin' __plugin_kind__ = 'Configuraciones' __implements__ = Machine def __init__(self, id): self.id = id (other methods) manage_addMiPluginForm = DTMLFile('addMiPlugin', globals()) def manage_addMiPlugin(self, id, REQUEST=None): """ Creamos una maquina""" obj = miPlugin(id) return self.Destination()._installPlugIn(obj, "Configurador, REQUEST) ############################################################### And in the __init__.py: def initialize(context): context.registerClass( foo, meta_type='foo', constructors = ( manage_addfooForm, manage_addfoo), icon = 'www/hada.png' ) context.registerPlugInClass( miPlugin, 'miMaquina', permission = 'add plugin miPlugin', constructors = (manage_addMiPluginForm, manage_addMiPlugin), ) The error that zope give me is: Error Type: AttributeError Error Value: __len__ ------ File /usr/local/Zope-2.4.1-linux2-x86/lib/python/App/Management.py, line 143, in manage_workspace (Object: PlugInBase) File /usr/local/Zope-2.4.1-linux2-x86/lib/python/App/Management.py, line 115, in filtered_manage_options (Object: PlugInBase) File /usr/local/Zope-2.4.1-linux2-x86/lib/python/Products/PlugIns/PlugIns.py, line 187, in manage_options (Object: PlugInBase) AttributeError: (see above) Can anybody help me? please