从类到装饰器的python自变量

Question

我正在尝试构建我的第一个装饰器并在类中实现它。

# decorator class
class Cache(object):
  def __init__(self,filename,**kwargs):
    self.time_ago = datetime.now() - timedelta(**kwargs)
    self.filename = filename

  def __call__(self,fn):
    if not os.path.isfile(self.filename):
      return self.cache(fn(self))

    time_ago = self.time_ago
    filename = self.filename
    c_age = datetime.fromtimestamp(os.path.getctime(filename))
    m_age = datetime.fromtimestamp(os.path.getmtime(filename))
    print (c_age)
    print (m_age)
    print (time_ago)
    if c_age < time_ago or m_age < time_ago:
      return self.cache(fn(self))
    else:
      return self.read()

  def cache(self,data):
      with open(self.filename,'r+') as ef:
        ef.write(data)
        return ef.read()

  def read(self):
    f = open(self.filename,'r')
    data = f.read()
    f.close()
    return data

我正在尝试在下面的类中调用装饰器:

class Zabb(object):

  @Cache('nodes.json',minutes=1)
  def getNodes(self):
    return "Get Nodes"

我这样调用它:

z = Zabb()
nodes = z.getNodes()

我收到以下错误:

Traceback (most recent call last):
File "./deco.py", line 52, in <module>
nodes = z.getNodes()
TypeError: 'str' object is not callable

我即将完成这项工作。我做错了什么？

Answer 1

您需要从 __call__ 方法返回一个高阶函数(包装)。添加一个内部方法并返回它。

def __call__(self, fn):
    def wrapper(*args, **kwargs): # <-- Add this wrapper
        if not os.path.isfile(self.filename):
            return self.cache(fn(*args, **kwargs))

        time_ago = self.time_ago
        filename = self.filename
        c_age = datetime.fromtimestamp(os.path.getctime(filename))
        m_age = datetime.fromtimestamp(os.path.getmtime(filename))
        print (c_age)
        print (m_age)
        print (time_ago)
        if c_age < time_ago or m_age < time_ago:
            return self.cache(fn(*args, **kwargs))
        else:
            return self.read()
    return wrapper # <-- Return the wrapper