python - 在类中使用装饰器

Question

我正在尝试在我的应用程序中实现一个简单的日志记录功能。

class messages(object):

    # Implement decorator here
    def on(self):
        def wrapper():
            # Do something here
        return wrapper

    def off(self):
        def wrapper():
            # Do something here
        return wrapper


class website(object):

    @messages.on #This line can be switched on/off
    def login(self):
        # Do a whole bunch of stuff here
        self.response = "[+] Login Succeeded!"

website = website()
website.login() # prints self.response based on @messages.on/off

但我不确定我需要在我的装饰器中应用什么。我尝试过创建实例并添加参数，但大多数情况下都会收到 TypeError。我对装饰器相当陌生。任何帮助将不胜感激，我很乐意下次记住这一点。

Answer 1

1. 如果您只想让狗吠叫(如示例中所示)，则无需启用装饰器

   class Dog(object):
       def __init__(self):
           self.sound = "Woof!"
   
       def bark(self):
           return self.sound
   

2. 如果您想为类中的某些函数启用日志记录，可以使用以下代码来实现此目的，并在注释中进行说明

   from functools import wraps
   
   class Utilities(object):
   
       @staticmethod  # no default first argument in logger function
       def logger(f):  # accepts a function
           @wraps(f)  # good practice https://docs.python.org/2/library/functools.html#functools.wraps
           def wrapper(self, *args, **kwargs):  # explicit self, which means this decorator better be used inside classes only
               print("Before:", self.sound)
               result = f(self, *args, **kwargs)
               print("After:", self.sound)
               return result
           return wrapper
   
   
   class Dog(object):
       def __init__(self):
           self.sound = "Woof!"
   
       @Utilities.logger
       def run(self):
           """Perform running movement"""
           print("Running")
   

示例:

>>> dog = Dog()
>>> dog.run()
Before: Woof!
Running
After: Woof!

尽管毕竟没有必要在 Utilities 类中存储装饰器功能 - 最好有一个名为 utils 的单独模块(文件)并将装饰器放在那里作为独立功能