多个python装饰器

Question

我有一个装饰方法（my_method）的Django模型（MyModel）。 我期待装饰对my_method进行一些检查：

• 如果检查成功，my_method应该返回一个字符串;

• 如果检查不成功，my_method应返回装饰器返回的失败消息。

的逻辑如下：

# models.py 
class MyModel(models.Model): 
    @decorator1 
    @decorator2 
    def my_method(self, request, *args, **kwargs): 
     return u'The result that must be returned if all the checks performed by the decorator succeed' 


# decorators.py 
from functools import wraps 

# decorator1 checks if certain conditions are met. If yes, it returns the decorated method (method_to_decorate); if not, it returns a tuple 
def decorator1(method_to_decorate): 
    @wraps(method_to_decorate) 
    def wrapper1(self, request, *args, **kwargs): 
     if a_condition : 
      return method_to_decorate(self, request, *args, **kwargs) 
     else: 
      # we return a failure message 
      return ('failure', 'message') 
    return wrapper1 

# in decorator2, we want to know if the check performed by decorator1 was successful 
# in case of success, we perform decorator2's check 
# in case of failure, decorator2 should simply pass the failure message returned by decorator1 
def decorator2(method_to_decorate): 
    @wraps(method_to_decorate) 
    def wrapper2(self, request, *args, **kwargs): 

     # if the first decorator succeeded 
     if decorator1_s_test_was_successful: 
      # we check if the conditions of the second decorator are met 
      if decorator2_s_test_was_successful: 
       # we return the method 
       return method_to_decorate(self, request, *args, **kwargs) 
      else: 
       # we return a failure message 
       return ('another failure', 'message') 
    # if the first decorator did not succeed 
     else: # decorator1 returned a tuple : ('failure', 'message') 
      return the_failure_that_decorator1_returned 
    return wrapper2 

所以，如果decorator1返回一个失败，我期望an_instance_of_my_model_instance.my_method（请求）返回（ '故障'， '消息'）。如果decorator1成功但不是decorator2，我会期待（'另一个失败'，'消息'）。如果所有的测试都通过了，那么如果装饰器执行的所有检查都成功，就必须返回结果'

如果decorator1的检查成功通过，我不知道如何检查装饰器2。我试图通过检查decorator2中method_to_decorate的类型（）来完成它，但似乎该类型使用原始方法本身，而不是decorator1返回的结果（就像装饰器不知道以前装饰器所执行的操作一样） 。

预先感谢您！

Answer 1

，如果你想decorator2检查了在你需要交换的@decorator1和@decorator2线无论decorator1返回：

@decorator2 
@decorator1 
def my_method(self, request, *args, **kwargs): 
    return u'The result that must be returned if all the checks performed by the decorator succeed' 

现在decorator2将包裹任何方法decorator1返回，这样的话你可以检查那个方法返回。

def decorator2(method_to_decorate): 
    @wraps(method_to_decorate) 
    def wrapper2(self, request, *args, **kwargs): 

     result = method_to_decorate(self, request, *args, **kwargs) 

     if isinstance(result, tuple) and result and result[0] == 'failure': 
      # decorator1 returned a failure 
      return result 
     else: 
      # decorator1 passed through the wrapped method call 
      if decorator2_s_test_was_successful: 
       return result 
      else: 
       return ('another failure', 'message') 

    return wrapper2 

Answer 2

的装饰会叫你把它们装饰方法上面的顺序，并给予你的程序结构，decorator2不会被调用，如果decorator1失败，所以没有必要检查是否decorator1是成功的decorator2。

稍微简单的例子...

from functools import wraps 


def decorator1(f): 
    @wraps(f) 
    def wrapper(a): 
     if a >= 1: 
      return f(a) 
     return 'failed in decorator 1' 
    return wrapper 

def decorator2(f): 
    @wraps(f) 
    def wrapper(a): 
     if a >= 2: 
      return f(a) 
     return 'failed in decorator 2' 
    return wrapper 

@decorator1 
@decorator2 
def my_func(a): 
    return 'success' 


print my_func(0) 
print my_func(1) 
print my_func(2) 

...它打印...

failed in decorator 1 
failed in decorator 2 
success