"""Component architecture for Twisted."""
import reflect, util, context
from twisted.persisted import styles
import types
import warnings
import weakref
ALLOW_DUPLICATES = 0
class _Nothing:
"""
An alternative to None - default value for functions which raise if default not passed.
"""
class _NoImplementor:
"""
Same as _Nothing but used by MetaInterface.__call__
"""
def getRegistry(r):
if r is None:
return context.get(AdapterRegistry, theAdapterRegistry)
else:
return r
class CannotAdapt(NotImplementedError):
"""
Can't adapt some object to some Interface.
"""
pass
class MetaInterface(type):
def __call__(self, adaptable, default=_Nothing, persist=None, registry=None):
"""
Try to adapt `adaptable' to self; return `default' if it was passed, otherwise
raise L{CannotAdapt}.
"""
adapter = default
registry = getRegistry(registry)
if (persist is None or persist) and hasattr(adaptable, 'getComponent'):
adapter = adaptable.getComponent(self, registry, default=_NoImplementor)
else:
adapter = registry.getAdapter(adaptable, self, _NoImplementor,
persist=persist)
if adapter is _NoImplementor:
if hasattr(self, '__adapt__'):
adapter = self.__adapt__.im_func(adaptable, default)
else:
adapter = default
if adapter is _Nothing:
raise CannotAdapt("%s cannot be adapted to %s." %
(adaptable, self))
return adapter
class Interface:
"""Base class for interfaces.
Interfaces define and document an interface for a class. An interface
class's name must begin with I, and all its methods should have no
implementation code.
Objects that implement an interface should have an attribute __implements__,
that should be either an Interface subclass or a tuple, or tuple of tuples,
of such Interface classes.
A class whose instances implement an interface should list the interfaces
its instances implement in a class-level __implements__.
For example::
| class IAdder(Interface):
| 'Objects implementing this interface can add objects.'
|
| def add(self, a, b):
| 'Add two objects together and return the result.'
|
| class Adder:
|
| __implements__ = IAdder
|
| def add(self, a, b):
| return a + b
You can call an Interface with a single argument; If the passed object can
be adapted to the Interface in some way, the adapter will be returned.
"""
__metaclass__ = MetaInterface
def adaptWith(self, using, to, registry=None):
registry = getRegistry(registry)
registry.registerAdapter(using, self, to)
adaptWith = classmethod(adaptWith)
def tupleTreeToList(t, l=None):
"""Convert an instance, or tree of tuples, into list."""
if l is None: l = []
if isinstance(t, types.TupleType):
for o in t:
tupleTreeToList(o, l)
else:
l.append(t)
return l
def implements(obj, interfaceClass):
"""Return boolean indicating if obj implements the given interface."""
if not hasattr(obj, '__implements__'):
return 0
for i in tupleTreeToList(obj.__implements__):
if issubclass(i, interfaceClass):
return 1
return 0
def getInterfaces(obj, attr='__implements__'):
"""Return list of all interfaces an object implements, using a particular
attribute name. For example, if you wish to discover what interfaces a
class implements directly, pass '__class_implements__' as the attribute
name.
"""
if not hasattr(obj, attr):
return []
result = []
for i in tupleTreeToList(getattr(obj,attr,())):
result.append(i)
result.extend(reflect.allYourBase(i, Interface))
result = util.uniquify(result)
result.remove(Interface)
return result
def superInterfaces(interface):
"""Given an interface, return list of super-interfaces (including itself)."""
result = [interface]
result.extend(reflect.allYourBase(interface, Interface))
result = util.uniquify(result)
result.remove(Interface)
return result
def classToInterfaces(k):
l = getInterfaces(k)
l.insert(0, k)
return l
class _Wrapper(object):
"""Makes any object be able to be dict key."""
__slots__ = ["a"]
def __init__(self, a):
self.a = a
class AdapterRegistry:
def __init__(self):
self.adapterRegistry = {}
self.adapterPersistence = weakref.WeakValueDictionary()
self.adapterOrigPersistence = weakref.WeakValueDictionary()
def persistAdapter(self, original, iface, adapter):
self.adapterPersistence[(id(original), iface)] = adapter
self.adapterOrigPersistence[_Wrapper(original)] = adapter
def registerAdapter(self, adapterFactory, origInterface, *interfaceClasses):
"""Register an adapter class.
An adapter class is expected to implement the given interface, by
adapting instances implementing 'origInterface'. An adapter class's
__init__ method should accept one parameter, an instance implementing
'origInterface'.
"""
assert interfaceClasses, "You need to pass an Interface"
global ALLOW_DUPLICATES
for interfaceClass in interfaceClasses:
if (self.adapterRegistry.has_key((origInterface, interfaceClass))
and not ALLOW_DUPLICATES):
raise ValueError(
"an adapter (%s) was already registered." % (
self.adapterRegistry[(origInterface, interfaceClass)]
)
)
if not issubclass(interfaceClass, Interface):
raise ValueError, "interface %s doesn't inherit from %s" % (interfaceClass, Interface)
for i in superInterfaces(interfaceClass):
if not self.adapterRegistry.has_key((origInterface, i)):
self.adapterRegistry[(origInterface, i)] = adapterFactory
def getAdapterFactory(self, fromInterface, toInterface, default):
"""Return registered adapter for a given class and interface.
"""
return self.adapterRegistry.get((fromInterface, toInterface), default)
getAdapterClass = getAdapterFactory
def getAdapterClassWithInheritance(self, klass, interfaceClass, default):
"""Return registered adapter for a given class and interface.
"""
adapterClass = self.adapterRegistry.get((klass, interfaceClass), _Nothing)
if adapterClass is _Nothing:
for baseClass in reflect.allYourBase(klass):
adapterClass = self.adapterRegistry.get((baseClass, interfaceClass),
_Nothing)
if adapterClass is not _Nothing:
return adapterClass
else:
return adapterClass
return default
def getAdapter(self, obj, interfaceClass, default=_Nothing,
adapterClassLocator=None, persist=None):
"""Return an object that implements the given interface.
The result will be a wrapper around the object passed as a parameter, or
the parameter itself if it already implements the interface. If no
adapter can be found, the 'default' parameter will be returned.
"""
if implements(obj, interfaceClass):
return obj
if persist != False:
pkey = (id(obj), interfaceClass)
if self.adapterPersistence.has_key(pkey):
return self.adapterPersistence[pkey]
if hasattr(obj, '__class__'):
klas = obj.__class__
else:
klas = type(obj)
for fromInterface in classToInterfaces(klas):
adapterFactory = ( (adapterClassLocator or self.getAdapterFactory)(
fromInterface, interfaceClass, None) )
if adapterFactory is not None:
adapter = adapterFactory(obj)
if persist:
self.persistAdapter(obj, interfaceClass, adapter)
return adapter
if default is _Nothing:
raise NotImplementedError('%s instance does not implement %s, and '
'there is no registered adapter.' %
(obj, interfaceClass))
return default
theAdapterRegistry = AdapterRegistry()
registerAdapter = theAdapterRegistry.registerAdapter
getAdapterClass = theAdapterRegistry.getAdapterClass
getAdapterClassWithInheritance = theAdapterRegistry.getAdapterClassWithInheritance
getAdapter = theAdapterRegistry.getAdapter
class Adapter:
"""I am the default implementation of an Adapter for some interface.
This docstring contains a limerick, by popular demand::
Subclassing made Zope and TR
much harder to work with by far.
So before you inherit,
be sure to declare it
Adapter, not PyObject*
@cvar temporaryAdapter: If this is True, the adapter will not be
persisted on the Componentized.
@cvar multiComponent: If this adapter is persistent, should it be
automatically registered for all appropriate interfaces.
"""
temporaryAdapter = 0
multiComponent = 1
def __init__(self, original):
"""Set my 'original' attribute to be the object I am adapting.
"""
self.original = original
def getComponent(self, interface, registry=None, default=None):
"""
I forward getComponent to self.original if it has it, otherwise I
simply return default.
"""
try:
f = self.original.getComponent
except AttributeError:
return default
else:
return f(interface, registry=registry, default=default)
def isuper(self, iface, adapter):
"""
Forward isuper to self.original
"""
return self.original.isuper(iface, adapter)
class Componentized(styles.Versioned):
"""I am a mixin to allow you to be adapted in various ways persistently.
I define a list of persistent adapters. This is to allow adapter classes
to store system-specific state, and initialized on demand. The
getComponent method implements this. You must also register adapters for
this class for the interfaces that you wish to pass to getComponent.
Many other classes and utilities listed here are present in Zope3; this one
is specific to Twisted.
"""
persistenceVersion = 1
def __init__(self):
self._adapterCache = {}
def locateAdapterClass(self, klass, interfaceClass, default, registry=None):
return getRegistry(registry).getAdapterClassWithInheritance(klass, interfaceClass, default)
def setAdapter(self, interfaceClass, adapterClass):
self.setComponent(interfaceClass, adapterClass(self))
def addAdapter(self, adapterClass, ignoreClass=0, registry=None):
"""Utility method that calls addComponent. I take an adapter class and
instantiate it with myself as the first argument.
@return: The adapter instantiated.
"""
adapt = adapterClass(self)
self.addComponent(adapt, ignoreClass, registry)
return adapt
def setComponent(self, interfaceClass, component):
"""
"""
self._adapterCache[reflect.qual(interfaceClass)] = component
def addComponent(self, component, ignoreClass=0, registry=None):
"""
Add a component to me, for all appropriate interfaces.
In order to determine which interfaces are appropriate, the component's
__implements__ attribute will be scanned.
If the argument 'ignoreClass' is True, then all interfaces are
considered appropriate.
Otherwise, an 'appropriate' interface is one for which its class has
been registered as an adapter for my class according to the rules of
getComponent.
@return: the list of appropriate interfaces
"""
for iface in tupleTreeToList(component.__implements__):
if (ignoreClass or
(self.locateAdapterClass(self.__class__, iface, None, registry)
== component.__class__)):
self._adapterCache[reflect.qual(iface)] = component
def unsetComponent(self, interfaceClass):
"""Remove my component specified by the given interface class."""
del self._adapterCache[reflect.qual(interfaceClass)]
def removeComponent(self, component):
"""
Remove the given component from me entirely, for all interfaces for which
it has been registered.
@return: a list of the interfaces that were removed.
"""
if (isinstance(component, types.ClassType) or
isinstance(component, types.TypeType)):
warnings.warn("passing interface to removeComponent, you probably want unsetComponent", DeprecationWarning, 1)
self.unsetComponent(component)
return [component]
l = []
for k, v in self._adapterCache.items():
if v is component:
del self._adapterCache[k]
l.append(reflect.namedObject(k))
return l
def getComponent(self, interface, registry=None, default=None):
"""Create or retrieve an adapter for the given interface.
If such an adapter has already been created, retrieve it from the cache
that this instance keeps of all its adapters. Adapters created through
this mechanism may safely store system-specific state.
If you want to register an adapter that will be created through
getComponent, but you don't require (or don't want) your adapter to be
cached and kept alive for the lifetime of this Componentized object,
set the attribute 'temporaryAdapter' to True on your adapter class.
If you want to automatically register an adapter for all appropriate
interfaces (with addComponent), set the attribute 'multiComponent' to
True on your adapter class.
"""
registry = getRegistry(registry)
k = reflect.qual(interface)
if self._adapterCache.has_key(k):
return self._adapterCache[k]
elif implements(self, interface):
return self
else:
adapter = registry.getAdapter(self, interface, default,
lambda k, ik, d:
self.locateAdapterClass(k, ik, d, registry))
if adapter is not None and adapter is not _Nothing and not (
hasattr(adapter, "temporaryAdapter") and
adapter.temporaryAdapter):
self._adapterCache[k] = adapter
if (hasattr(adapter, "multiComponent") and
adapter.multiComponent and
hasattr(adapter, '__implements__')):
self.addComponent(adapter)
return adapter
def upgradeToVersion1(self):
for (k, v) in self._adapterCache.items():
self._adapterCache[reflect.qual(k)] = v
class ReprableComponentized(Componentized):
def __init__(self):
Componentized.__init__(self)
def __repr__(self):
from cStringIO import StringIO
from pprint import pprint
sio = StringIO()
pprint(self._adapterCache, sio)
return sio.getvalue()
__all__ = ["Interface", "implements", "getInterfaces", "superInterfaces",
"registerAdapter", "getAdapterClass", "getAdapter", "Componentized",
"AdapterRegistry", "Adapter", "ReprableComponentized"]