在 python 中你想要的通常实现是这样的:
class CallProxy(object):
'this class wraps a callable in an object'
def __init__(self, fun):
self.fun = fun
def __call__(self, *args, **kwargs):
return self.fun(*args, **kwargs)
class ObjProxy(object):
''' a proxy object intercepting attribute access
'''
def __init__(self, obj):
self.__dict__['_ObjProxy__obj'] = obj
def __getattr__(self, name):
attr = getattr(self.__obj, name)
if callable(attr):
return CallProxy(attr)
else:
return attr
def __setattr__(self, name, value):
setattr(self.__obj, name, value)
我写了一个测试来证明这符合预期:
#keep a list of calls to the TestObj for verification
call_log = list()
class TestObj(object):
''' test object on which to prove
that the proxy implementation is correct
'''
def __init__(self):
#example attribute
self.a = 1
self._c = 3
def b(self):
'example method'
call_log.append('b')
return 2
def get_c(self):
call_log.append('get_c')
return self._c
def set_c(self, value):
call_log.append('set_c')
self._c = value
c = property(get_c, set_c, 'example property')
def verify(obj, a_val, b_val, c_val):
'testing of the usual object semantics'
assert obj.a == a_val
obj.a = a_val + 1
assert obj.a == a_val + 1
assert obj.b() == b_val
assert call_log[-1] == 'b'
assert obj.c == c_val
assert call_log[-1] == 'get_c'
obj.c = c_val + 1
assert call_log[-1] == 'set_c'
assert obj.c == c_val + 1
def test():
test = TestObj()
proxy = ObjProxy(test)
#check validity of the test
verify(test, 1, 2, 3)
#check proxy equivalent behavior
verify(proxy, 2, 2, 4)
#check that change is in the original object
verify(test, 3, 2, 5)
if __name__ == '__main__':
test()
这在 CPython 上执行,没有任何断言抛出异常。IronPython 应该是等价的,否则它会被破坏并且这个测试应该被添加到它的单元测试套件中。