我已经定义了一个类，该类将装饰器定义为该类的方法。装饰器本身会创建第二个类的可调用实例，以替换装饰的方法。由于修饰的方法现在实际上是一个类，因此可以在其上调用方法。在我的（虚构的，最小的）示例中，我想使用每个方法自定义的最大回调数来注册回调。
class CallbackAcceptor:
def __init__(self, max_num_callbacks, func):
self._func = func
self._max_num_callbacks = max_num_callbacks
self._callbacks = []
def __call__(self, *args, **kwargs):
# This ends up being called when the decorated method is called
for callback in self._callbacks:
print(f"Calling {callback.__name__}({args}, {kwargs})")
callback(*args, **kwargs)
return self._func(*args, **kwargs) # this line is the problem, self is not bound
def register_callback(self, func):
# Here I can register another callback for the decorated function
if len(self._callbacks) < self._max_num_callbacks:
self._callbacks.append(func)
else:
raise RuntimeError(f"Can not register any more callbacks for {self._func.__name__}")
return func
class MethodsWithCallbacksRegistry:
def __init__(self):
self.registry = {} # Keep track of everything that accepts callbacks
def accept_callbacks(self, max_num_callbacks: int = 1):
def _make_accept_callbacks(func):
# Convert func to an CallbackAcceptor instance so we can register callbacks on it
if func.__name__ not in self.registry:
self.registry[func.__name__] = CallbackAcceptor(max_num_callbacks=max_num_callbacks, func=func)
return self.registry[func.__name__]
return _make_accept_callbacks
所有功能都按预期工作，但是当我装饰一个类方法时，它会中断，因为类实例未绑定到装饰的方法上：
registry = MethodsWithCallbacksRegistry()
@registry.accept_callbacks(max_num_callbacks=1)
def bar(i):
return i * 10
@bar.register_callback
def bar_callback(*args, **kwargs):
print("Bar Callback")
print(bar(i=10)) # Works fine, prints "Bar Callback" and then 100
现在，如果我定义了一种接受回调的方法：
class Test:
@registry.accept_callbacks(max_num_callbacks=1)
def foo(self, i):
return i * 2
@Test.foo.register_callback
def foo_callback(*args, **kwargs):
print("Foo Callback")
如果我显式地传递自己，则有效，但如果我仅假定实例已绑定，则无效：
t = Test()
# Note that I pass the instance of t explicitly as self
Test.foo(t, i=5) # Works, prints "Foo Callback" and then 10
t.foo(t, i=5) # Works, prints "Foo Callback" and then 10
t.foo(i=5) # Crashes, because self is not passed to foo
这是回溯：
Traceback (most recent call last):
File "/home/veith/.PyCharmCE2019.3/config/scratches/scratch_4.py", line 62, in <module>
t.foo(i=5)
File "/home/veith/.PyCharmCE2019.3/config/scratches/scratch_4.py", line 13, in __call__
return self._func(*args, **kwargs) # this line is the problem, self is not bound
TypeError: foo() missing 1 required positional argument: 'self'
尽管我总是认为t.foo(i=5)基本上是通过描述符对Test.foo(t, i=5)的语法糖，但似乎我是错的。所以这是我的问题：
谢谢！
PS：我正在使用python 3.8
如果将CallbackAcceptor设置为descriptor，则其工作方式如下：
class CallbackAcceptor:
def __init__(self, max_num_callbacks, func):
self._func = func
self._max_num_callbacks = max_num_callbacks
self._callbacks = []
def __call__(self, *args, **kwargs):
# This ends up being called when the decorated method is called
for callback in self._callbacks:
print(f"Calling {callback.__name__}({args}, {kwargs})")
callback(*args, **kwargs)
return self._func(*args, **kwargs)
def register_callback(self, func):
# Here I can register another callback for the decorated function
if len(self._callbacks) < self._max_num_callbacks:
self._callbacks.append(func)
else:
raise RuntimeError(f"Can not register any more callbacks for {self._func.__name__}")
return func
# Implementing __get__ makes this a descriptor
def __get__(self, obj, objtype=None):
if obj is not None:
# the call is made on an instance, we can pass obj as the self of the function that will be called
return functools.partial(self.__call__, obj)
# Called on a class or a raw function, just return self so we can register more callbacks
return self
现在正在按预期方式拨打电话：
print(bar(i=10))
# Bar Callback
# 100
t = Test()
t.foo(i=5)
# Foo Callback
# 10
t.foo(t, i=5)
# TypeError: foo() got multiple values for argument 'i'