def providedBy(ob):
# Here we have either a special object, an old-style declaration
# or a descriptor
# Try to get __providedBy__
try:
r = ob.__providedBy__
except AttributeError:
# Not set yet. Fall back to lower-level thing that computes it
return getObjectSpecification(ob)
try:
# We might have gotten a descriptor from an instance of a
# class (like an ExtensionClass) that doesn't support
# descriptors. We'll make sure we got one by trying to get
# the only attribute, which all specs have.
r.extends
except AttributeError:
# The object's class doesn't understand descriptors.
# Sigh. We need to get an object descriptor, but we have to be
# careful. We want to use the instance's __provides__, if
# there is one, but only if it didn't come from the class.
try:
r = ob.__provides__
except AttributeError:
# No __provides__, so just fall back to implementedBy
return implementedBy(ob.__class__)
# We need to make sure we got the __provides__ from the
# instance. We'll do this by making sure we don't get the same
# thing from the class:
try:
cp = ob.__class__.__provides__
except AttributeError:
# The ob doesn't have a class or the class has no
# provides, assume we're done:
return r
if r is cp:
# Oops, we got the provides from the class. This means
# the object doesn't have it's own. We should use implementedBy
return implementedBy(ob.__class__)
return r
def __get__(self, inst, cls):
"""Get an object specification for an object
For example::
>>> from zpt._zope.interface import Interface
>>> class IFoo(Interface): pass
...
>>> class IFooFactory(Interface): pass
...
>>> class C(object):
... implements(IFoo)
... classProvides(IFooFactory)
>>> [i.getName() for i in C.__providedBy__]
['IFooFactory']
>>> [i.getName() for i in C().__providedBy__]
['IFoo']
"""
# Get an ObjectSpecification bound to either an instance or a class,
# depending on how we were accessed.
if inst is None:
return getObjectSpecification(cls)
provides = getattr(inst, '__provides__', None)
if provides is not None:
return provides
return implementedBy(cls)
def getObjectSpecification(ob):
provides = getattr(ob, '__provides__', None)
if provides is not None:
return provides
try:
cls = ob.__class__
except AttributeError:
# We can't get the class, so just consider provides
return _empty
return implementedBy(cls)
def classImplementsOnly(cls, *interfaces):
"""Declare the only interfaces implemented by instances of a class
The arguments after the class are one or more interfaces or
interface specifications (IDeclaration objects).
The interfaces given (including the interfaces in the
specifications) replace any previous declarations.
Consider the following example::
>>> from zpt._zope.interface import Interface
>>> class I1(Interface): pass
...
>>> class I2(Interface): pass
...
>>> class I3(Interface): pass
...
>>> class I4(Interface): pass
...
>>> class A(object):
... implements(I3)
>>> class B(object):
... implements(I4)
>>> class C(A, B):
... pass
>>> classImplementsOnly(C, I1, I2)
>>> [i.getName() for i in implementedBy(C)]
['I1', 'I2']
Instances of ``C`` provide only ``I1``, ``I2``, and regardless of
whatever interfaces instances of ``A`` and ``B`` implement.
"""
spec = implementedBy(cls)
spec.__bases__ = tuple(_normalizeargs(interfaces))
spec.inherit = None
def __init__(self, cls, metacls, *interfaces):
self._cls = cls
self._implements = implementedBy(cls)
self.__args = (cls, metacls, ) + interfaces
Declaration.__init__(self, *(interfaces + (implementedBy(metacls), )))
def classImplements(cls, *interfaces):
"""Declare additional interfaces implemented for instances of a class
The arguments after the class are one or more interfaces or
interface specifications (IDeclaration objects).
The interfaces given (including the interfaces in the
specifications) are added to any interfaces previously
declared.
Consider the following example::
for example:
>>> from zpt._zope.interface import Interface
>>> class I1(Interface): pass
...
>>> class I2(Interface): pass
...
>>> class I3(Interface): pass
...
>>> class I4(Interface): pass
...
>>> class I5(Interface): pass
...
>>> class A(object):
... implements(I3)
>>> class B(object):
... implements(I4)
>>> class C(A, B):
... pass
>>> classImplements(C, I1, I2)
>>> [i.getName() for i in implementedBy(C)]
['I1', 'I2', 'I3', 'I4']
>>> classImplements(C, I5)
>>> [i.getName() for i in implementedBy(C)]
['I1', 'I2', 'I5', 'I3', 'I4']
Instances of ``C`` provide ``I1``, ``I2``, ``I5``, and whatever
interfaces instances of ``A`` and ``B`` provide.
"""
spec = implementedBy(cls)
spec.declared += tuple(_normalizeargs(interfaces))
# compute the bases
bases = []
seen = {}
for b in spec.declared:
if b not in seen:
seen[b] = 1
bases.append(b)
if spec.inherit is not None:
for c in spec.inherit.__bases__:
b = implementedBy(c)
if b not in seen:
seen[b] = 1
bases.append(b)
spec.__bases__ = tuple(bases)
def implementedByFallback(cls):
"""Return the interfaces implemented for a class' instances
The value returned is an IDeclaration.
for example:
>>> from zpt._zope.interface import Interface
>>> class I1(Interface): pass
...
>>> class I2(I1): pass
...
>>> class I3(Interface): pass
...
>>> class I4(I3): pass
...
>>> class C1(object):
... implements(I2)
>>> class C2(C1):
... implements(I3)
>>> [i.getName() for i in implementedBy(C2)]
['I3', 'I2']
"""
# This also manages storage of implementation specifications
try:
spec = cls.__dict__.get('__implemented__')
except AttributeError:
# we can't get the class dict. This is probably due to a
# security proxy. If this is the case, then probably no
# descriptor was installed for the class.
# We don't want to depend directly on zpt._zope.security in
# zpt._zope.interface, but we'll try to make reasonable
# accommodations in an indirect way.
# We'll check to see if there's an implements:
spec = getattr(cls, '__implemented__', None)
if spec is None:
# There's no spec stred in the class. Maybe its a builtin:
spec = BuiltinImplementationSpecifications.get(cls)
if spec is not None:
return spec
return _empty
if spec.__class__ == Implements:
# we defaulted to _empty or there was a spec. Good enough.
# Return it.
return spec
# TODO: need old style __implements__ compatibility?
# Hm, there's an __implemented__, but it's not a spec. Must be
# an old-style declaration. Just compute a spec for it
return Declaration(*_normalizeargs((spec, )))
if isinstance(spec, Implements):
return spec
if spec is None:
spec = BuiltinImplementationSpecifications.get(cls)
if spec is not None:
return spec
# TODO: need old style __implements__ compatibility?
if spec is not None:
# old-style __implemented__ = foo declaration
spec = (spec, ) # tuplefy, as it might be just an int
spec = Implements(*_normalizeargs(spec))
spec.inherit = None # old-style implies no inherit
del cls.__implemented__ # get rid of the old-style declaration
else:
try:
bases = cls.__bases__
except AttributeError:
if not callable(cls):
raise TypeError("ImplementedBy called for non-factory", cls)
bases = ()
spec = Implements(*[implementedBy(c) for c in bases])
spec.inherit = cls
spec.__name__ = (getattr(cls, '__module__', '?') or '?') + \
'.' + cls.__name__
try:
cls.__implemented__ = spec
if not hasattr(cls, '__providedBy__'):
cls.__providedBy__ = objectSpecificationDescriptor
if (isinstance(cls, DescriptorAwareMetaClasses)
and
'__provides__' not in cls.__dict__):
# Make sure we get a __provides__ descriptor
cls.__provides__ = ClassProvides(
cls,
getattr(cls, '__class__', type(cls)),
)
except TypeError:
if not isinstance(cls, type):
raise TypeError("ImplementedBy called for non-type", cls)
BuiltinImplementationSpecifications[cls] = spec
return spec