def registerFacet(cls, facet, *ifaces):
"""Registers a facet for class cls.
The 'facet' argument is an adapter class which will be registered
using its interfaces specified in __implements__ argument.
Notes: the assigned key will have the name of the class cls.
:param cls:
:param facet:
:param ifaces: optional list of interfaces to attach
"""
if not hasattr(cls, '_facets'):
cls._facets = {}
if not ifaces:
raise ValueError("It is not possible to register a facet "
"without specifing an interface")
for iface in ifaces:
if not isinstance(iface, InterfaceClass):
raise TypeError('iface must be an Interface')
if qual(iface) in cls._facets.keys():
raise TypeError(
'%s does already have a facet for interface %s' %
(cls.__name__, iface.__name__))
cls._facets[qual(iface)] = facet
def _adapter_hook(iface, obj):
# Twisted's IPathImportMapper occasionally sends in None
# which breaks isinstance, work-around. Johan 2008-09-29
if not isinstance(obj, Adaptable):
return
name = qual(iface)
adapterCache = getattr(obj, '_adapterCache', {})
if name in adapterCache:
return adapterCache[name]
try:
obj.getFacetType(iface)
except LookupError:
# zope.interface will handle this and raise TypeError,
# see InterfaceClass.__call__ in zope/interface/interface.py
return None
def getFacetType(cls, iface):
"""Fetches a facet type associated with an interface, or raise
LookupError if the facet type cannot be found.
:param iface: interface name for the facet to grab
:returns: the facet type for the interface
"""
facets = getattr(cls, '_facets', [])
iface_str = qual(iface)
if not iface_str in facets:
raise LookupError(
"%s doesn't have a facet for interface %s" %
(cls.__name__, iface.__name__))
return facets[iface_str]
def removeFacet(self, iface, *args, **kwargs):
"""Removes a facet from the current object
:param iface: interface of the facet to remove
"""
if not isinstance(iface, InterfaceClass):
raise TypeError('iface must be an Interface')
facets = self.__class__._facets
if not iface in facets:
raise AdapterError('%s does not have a facet for interface %s' %
(self.__class__.__name__, iface.__name__))
funcName = 'facet_%s_remove' % iface.__name__
func = getattr(self, funcName, None)
if func:
func(*args, **kwargs)
k = qual(iface)
del facets[k]
if k in self._adapterCache:
del self._adapterCache[k]
def addFacet(self, iface, *args, **kwargs):
"""Adds a facet implementing iface for the current object
:param iface: interface of the facet to add
:returns: the facet
"""
if isinstance(self, Adapter):
raise TypeError("An adapter can not be adapted to another "
"object.")
if not isinstance(iface, InterfaceClass):
raise TypeError('iface must be an Interface')
if not hasattr(self, '_adapterCache'):
self._adapterCache = {}
k = qual(iface)
if k in self._adapterCache:
raise AdapterError('%s already has a facet for interface %s' %
(self.__class__.__name__, iface.__name__))
facets = self.__class__._facets
funcName = 'facet_%s_add' % iface.__name__
func = getattr(self, funcName, None)
if func:
adapter = func(*args, **kwargs)
elif k in facets:
adapterClass = facets[k]
adapter = adapterClass(self, *args, **kwargs)
else:
raise AdapterError("The object type %s doesn't implement an "
"adapter for interface %s" % (type(self),
iface))
if adapter:
self._adapterCache[k] = adapter
return adapter
