Question

我想使用装饰器做一些准备工作并记录函数的状态，所以我写了类似的东西：

class Decorator:
    def __init__(self, func):
        self.count = 0
        self.func = func

    def __call__(self, *args, **kwargs):
        self.count += 1 # Simply count the call times
        return self.func(self, *args, **kwargs)

class Foo:
    def __init__(self):
        self.value = 0

    @Decorator
    def test(self, value):
        self.value = value # change the value of instance
        print(self.value)

f = Foo()
f.test(1)

print(f.value)
print(f.test.value)

但显而易见的是，self中的__call__(self, *args, **kwargs)对应Decorator的实例，而不是Foo的实例，这将使f.value保持不变，但f.test.value 1}}增加。

有什么方法可以将Foo的实例传递给Decorator而不是Decorator本身？

或者有没有办法更清楚地实现这个功能？

先谢谢。

Answer 1

由于装饰器只被调用一次并用一个Decorator类的实例替换所有实例的方法。它所做的就是：

Foo.test = Decorator(Foo.test)

这使得无法检测到被调用的实例。一个解决方法是手动在__init__ Foo中应用装饰器：

class Foo:
    def __init__(self):
        self.value = 0
        self.test = Decorator(self.test)

    def test(self, value):
        self.value = value # change the value of instance
        print(self.value)

这样装饰器会包装实例方法，因此您无需在self的{{1}}中传递__call__：

Decorator

现在它可以工作，你必须更新测试方法，因为class Decorator: def __init__(self, func): self.count = 0 self.func = func def __call__(self, *args, **kwargs): self.count += 1 # Simply count the call times return self.func(*args, **kwargs)不再存在：

f.test.value

按预期输出f = Foo() f.test(1) print(f.value)两次。

Answer 2

我得到了这个here

import functools

class Decorator(object):
    def __init__(self, func):
        self.count = 0
        self.func = func


    def __call__(self, *args, **kwargs):
        self.count += 1 # Simply count the call times
        return self.func( *args, **kwargs)

    def __get__(self, instance, instancetype):
        """Implement the descriptor protocol to make decorating instance 
        method possible.
        """

        # Return a partial function with the first argument is the instance 
        #   of the class decorated.
        return functools.partial(self.__call__, instance)



class Foo:
    def __init__(self):
        self.value = 0

    @Decorator
    def test(self, value):
        self.value = value # change the value of instance



f = Foo()
f.test(3)
print(f.value)  # prints 3


g = Foo()
g.test(8)
print(g.value) # prints 8

或可能是这个

def preJob(function): def updateToDo(self, *args, **kwargs): # do some recording function(self, *args, **kwargs) return updateToDo class Foo(object): def __init__(self): self.value = 0 @preJob def test(self, value): self.value = value f = Foo() f.test(3) print(f.value) # prints 3 g = Foo() g.test(8) print(g.value) # prints 8

Answer 3

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我发现使用Priyesh Kumar的答案，您可以将self参数从 call 方法简单地传递给要修饰的函数：

class threadSafeGenerator(object):
    """docstring for threadSafeGenerator"""
    class SafeGenerator(object):
        """docstring for SafeGenerator"""
        def __init__(self, iterable):
            self.iterable = iterable
            self.lock = Lock()
        def __iter__(self):
            return self

        def __next__(self):
            with self.lock:
                return next(self.iterable)

    def __init__(self, func):
        super(threadSafeGenerator, self).__init__()
        self.func = func

    def __call__(self, *args, **kwargs):
        return self.SafeGenerator(self.func(self, *args, **kwargs))

希望这会有所帮助！

编辑：没关系，仅当通过装饰器传递的函数未调用init方法中定义的类变量时才起作用

类作为类方法的装饰器

3 个答案: