Logout Support

Logout support is defined by a simple interface zope.authentication.interfaces.ILogout:

>>> from zope.authentication.interfaces import ILogout

that has a single ‘logout’ method.

The current use of ILogout is to adapt an zope.authentication.interfaces.IAuthentication instance to ILogout. To illustrate, we’ll create a simple logout implementation that adapts IAuthentication:

>>> from zope.component import adapter, provideAdapter
>>> from zope.interface import implementer
>>> from zope.authentication.interfaces import IAuthentication
>>> @adapter(IAuthentication)
... @implementer(ILogout)
... class SimpleLogout(object):
...     def __init__(self, auth):
...         pass
...     def logout(self, request):
...         print('User has logged out')

>>> provideAdapter(SimpleLogout)

and something to represent an authentication utility:

>>> @implementer(IAuthentication)
... class Authentication(object):
...     pass

>>> auth = Authentication()

To perform a logout, we adapt auth to ILogout and call ‘logout’:

>>> logout = ILogout(auth)
>>> request = object()
>>> logout.logout(request)
User has logged out

The ‘NoLogout’ Adapter

The zope.authentication.logout.NoLogout class can be registered as a fallback provider of ILogout for IAuthentication components that are not otherwise adaptable to ILogout. NoLogout’s logout method is a no-op.

>>> from zope.authentication.logout import NoLogout
>>> NoLogout(auth).logout(request)

Logout User Interface

Because some authentication protocols do not formally support logout, it may not be possible for a user to logout once he or she has logged in. In such cases, it would be inappropriate to present a user interface for logging out.

Because logout support is site-configurable, Zope provides an adapter that, when registered, indicates that the site is configured for logout. This class merely serves as a flag as it implements ILogoutSupported:

>>> from zope.authentication.logout import LogoutSupported
>>> from zope.authentication.interfaces import ILogoutSupported
>>> ILogoutSupported.implementedBy(LogoutSupported)
>>> ILogoutSupported.providedBy(LogoutSupported(request))