是否可以在由基礎 class 中定義的裝飾器生成的子 class 中檢索值？

Question

我有一個孩子 class 方法我想有條件地短路。 我想要做的是這樣的事情，除了我想將驗證邏輯放入基礎 class 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()

按照這個示例，我能夠將一些重復的代碼轉換為裝飾器模式。

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，我需要在裝飾器中調用基礎 class 的方法來進行驗證工作，並在子 class 中檢索 (validated) 的值。 按照這里的這個例子，我修改了裝飾器，試圖讓它調用 self.getvalue()。 此時它不會出錯，但它也不起作用，因為 self.getvalue() 不返回 True。 這開始看起來比它的價值更麻煩，但現在我很好奇它是否可能。

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()

是否可以使用裝飾器設置一個屬性，然后再檢索它？

                ...
                self.validated = True
                if not self.validated:
                    print "Not validated."
                    return
                ...
print work1.validated
                ...

AttributeError: 'ExtendedClass1' object has no attribute 'validated'

本質上，我想把它變成：

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

進入這個：

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 發布的建議，此示例滿足我的用例。 我仍然很想知道@validate 是否可以作為一種方法而不是獨立的 function 來實現，但這可以完成工作。

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, *args, **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()

Answer 1

@tponthieux，您可以做的是設置被調用的 function （方法）的屬性，然后檢索它：

簡單示例（更新）：

def validate(func):    
    def wrapped(self, *args, **kwargs):
        self.valid = True
        func(self, *args, **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

Answer 2

如果已驗證，僅調用裝飾方法怎么樣？ 如果您願意，可以傳遞validate方法的返回值：

class BaseClass(object):
    def getvalue(self):
        return True

    def validate(input_function):
        def wrapper(self, *args, **kwargs):
            self.validated = self.getvalue()
            if not self.validated:
                print "Not validated."
                return
            input_function(self, validated=self.validated, *args, **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=None):
        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()

這里的關鍵是將self添加到wrapper function 中。 發生的情況是您的裝飾函數沒有綁定到實例（並成為方法），而是由裝飾器（上例中的wrapper ）返回的 function 被綁定。 所以這個function會得到調用時傳入的self （實例）參數！ 重要的是要記住，@decorator 所做的只是調用decorator ，傳入你正在裝飾的@decorator ，然后用裝飾器返回的任何東西替換你正在裝飾的 function。 在您的示例中，這是wrapper ，對於 class，它與裝飾前的原始 function 沒有區別。

在上面的例子中，我明確地聲明了self 。 如果我們沒有，我們也可以從args中獲取它：

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, *args, **kwargs)

另請注意，我們將一個額外的關鍵字參數傳遞給包裝的方法，名為validated 。 這完全是可選的，您可以從示例中刪除validated=self.validated和validated=None部分。