是否有可能在由基类中定义的装饰器生成的子类中检索值？

分类：编程问答

如何解决是否有可能在由基类中定义的装饰器生成的子类中检索值？

| 我有一个孩子类方法，我想有条件地短路。我想做的是类似这样的事情，除了我想将验证逻辑放入基类中。 
class BaseClass(object):
    def getvalue(self):
        return True
    def validate(self):
        validated = self.getvalue()
        return validated

class ExtendedClass1(BaseClass):
    def do_some_work(self):
        validated = self.validate()
        if not validated:
            print \"Not validated.\"
            return
        print \"Things are validated if the method got this far.\",validated

class ExtendedClass2(BaseClass):
    def do_some_work(self):
        validated = self.validate()
        if not validated:
            print \"Not validated.\"
            return
        print \"Things are validated if the method got this far.\",validated

class ExtendedClass3(BaseClass):
    def do_some_work(self):
        print \"This one doesn\'t require validation.\"

work1 = ExtendedClass1()
work1.do_some_work()

work2 = ExtendedClass2()
work2.do_some_work()

work3 = ExtendedClass3()
work3.do_some_work()
在此示例之后，我能够将一些重复的代码转换为装饰器模式。 
class BaseClass(object):

    def validate(input_function):
        def wrapper(*args,**kwargs):
            validated = True
            if not validated:
                print \"Not validated.\"
                return
            input_function(*args,**kwargs)
        return wrapper

    validate = staticmethod(validate)

class ExtendedClass1(BaseClass):
    @BaseClass.validate
    def do_some_work(self):
        print \"Things are validated if the method got this far.\"

class ExtendedClass2(BaseClass):
    @BaseClass.validate
    def do_some_work(self):
        print \"Things are validated if the method got this far.\"

class ExtendedClass3(BaseClass):
    def do_some_work(self):
        print \"This one doesn\'t require validation.\"

work1 = ExtendedClass1()
work1.do_some_work()

work2 = ExtendedClass2()
work2.do_some_work()

work3 = ExtendedClass3()
work3.do_some_work()
但是，我需要在装饰器中调用基类的方法来进行验证工作，并在子类中检索（已验证）的值。在此示例之后，我修改了装饰器，以使其命名为self.getvalue（）。在这一点上，它不会出错，但是由于self.getvalue（）不会返回True，因此它也不起作用。看来这似乎已经超出了其应有的麻烦，但现在我很好奇是否可行。 
class BaseClass(object):

    def getvalue(self):
        return True

    def validate(self):
        def wrap(input_function):
            def wrapper(*args,**kwargs):
                validated = self.getvalue()
                if not validated:
                    print \"Not validated.\"
                    return
                input_function(*args,**kwargs)
            return wrapper
        return wrap

    validate = staticmethod(validate)

class ExtendedClass1(BaseClass):
    @BaseClass.validate
    def do_some_work(self):
        print \"Things are validated if the method got this far.\"#,validated

class ExtendedClass2(BaseClass):
    @BaseClass.validate
    def do_some_work(self):
        print \"Things are validated if the method got this far.\"#,validated

class ExtendedClass3(BaseClass):
    def do_some_work(self):
        print \"This one doesn\'t require validation.\"

work1 = ExtendedClass1()
work1.do_some_work()

work2 = ExtendedClass2()
work2.do_some_work()

work3 = ExtendedClass3()
work3.do_some_work()
是否可以使用装饰器设置属性，然后在以后检索它？ 
                ...
                self.validated = True
                if not self.validated:
                    print \"Not validated.\"
                    return
                ...
print work1.validated
                ...

AttributeError: \'ExtendedClass1\' object has no attribute \'validated\'
本质上，我想将其转为： 
class ExtendedClass1(BaseClass):
    def do_some_work(self):
        validated = self.validate()
        if not validated:
            print \"Not validated.\"
            return
        print \"Things are validated if the method got this far.\",validated
变成这个： 
class ExtendedClass1(BaseClass):
    @BaseClass.validate
    def do_some_work(self):
        print \"Things are validated if the method got this far.\",validated
使用Zaur Nasibov发表的建议，该示例满足了我的用例。我仍然想知道@validate是否可以作为方法而不是独立的函数实现，但这可以完成工作。 
class BaseClass(object):
    def getvalue(self):
        return True

def validate(func):
    def wrapped(self,*args,**kwargs):
        validated = self.getvalue()
        self.validated = validated
        if not validated:
            print \"Not validated.\"
            return
        func(self,**kwargs)
    return wrapped

class ExtendedClass1(BaseClass):
    @validate
    def do_some_work(self,input):
        print \"Things are validated if the method got this far.\",self.validated,input

class ExtendedClass2(BaseClass):
    @validate
    def do_some_work(self):
        print \"Things are validated if the method got this far.\",self.validated

class ExtendedClass3(BaseClass):
    def do_some_work(self):
        print \"This one doesn\'t require validation.\"#,self.validated

work1 = ExtendedClass1()
work1.do_some_work(input=\"some text\")

work2 = ExtendedClass2()
work2.do_some_work()

work3 = ExtendedClass3()
work3.do_some_work()
    

解决方法

        @tponthieux，您可以做的是设置被调用函数的属性（方法），然后检索它： 简单示例（更新）： 
def validate(func):    
    def wrapped(self,*args,**kwargs):
        self.valid = True
        func(self,**kwargs)
    return wrapped

class TestClass(object):
    @validate
    def do_some_work(self):
        print \"some work done\"

tc = TestClass()
tc.do_some_work()
print tc.valid
    ,        仅在经过验证的装饰方法上调用怎么办？如果愿意，可以传递
validate
方法的返回值： 
class BaseClass(object):
    def getvalue(self):
        return True

    def validate(input_function):
        def wrapper(self,**kwargs):
            self.validated = self.getvalue()
            if not self.validated:
                print \"Not validated.\"
                return
            input_function(self,validated=self.validated,**kwargs)
        return wrapper

    validate = staticmethod(validate)

class ExtendedClass1(BaseClass):
    @BaseClass.validate
    def do_some_work(self,validated=None):
        print \"Things are validated if the method got this far.\",validated

class ExtendedClass2(BaseClass):
    @BaseClass.validate
    def do_some_work(self,validated

class ExtendedClass3(BaseClass):
    def do_some_work(self):
        print \"This one doesn\'t require validation.\"

work1 = ExtendedClass1()
work1.do_some_work()

work2 = ExtendedClass2()
work2.do_some_work()

work3 = ExtendedClass3()
work3.do_some_work()
这里的关键是在
wrapper
功能上添加
self
。发生的事情是，您装饰的函数未绑定到实例（并成为方法），而是由装饰器（在上面的示例中为11）返回的函数被绑定。因此，此函数将获得调用时传递的
self
（实例）参数！重要的是要记住，
@decorator
所做的只是简单地调用
decorator
传递要修饰的函数，然后用修饰符返回的内容替换要修饰的函数。在您的示例中，这是
wrapper
，对于该类，装饰之前的功能与原始功能没有区别。 在上面的示例中，我明确声明了“ 10”。如果没有的话，我们也可以从
args
拿走它： 
def validate(input_function):
    def wrapper(*args,**kwargs):
        print \"args[0] is now the instance (conventionally called \'self\')\",args[0]
        self = args[0]
        self.validated = self.getvalue()
        if not self.validated:
            print \"Not validated.\"
            return
        input_function(validated=self.validated,**kwargs)
还要注意，我们向包装的方法传递了一个额外的关键字参数，名为
validated
。这是完全可选的，您可以从示例中删除
validated=self.validated
和
validated=None
部分。     

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