用装饰器继承

Question

这个问题是我在此处发布的上一个问题的扩展：link

我使用 Python 3.6.2。我有一个通用类 Framework 我的系统继承自它。

我使用装饰器on_initialize、on_event 和on_finalize 来通知Framework 每个方法必须在哪里执行。每个装饰器的参数precedence 用于确定每个部分的执行顺序（从低到高）。

# 3 decorators 
def on_initialize(precedence=0):
    def marker(func):
        func._initializer = precedence
        return func
    return marker


def on_event(precedence=0):
    def marker(func):
        func._event_handler = precedence
        return func
    return marker


def on_finalize(precedence=0):
    def marker(func):
        func._finalizer = precedence
        return func
    return marker

# Main framework
class Framework:

    def __init_subclass__(cls, *args, **kw):
        super().__init_subclass__(*args, **kw)
        handlers = dict(_initializer=[], _event_handler=[], _finalizer=[])
        for name, method in cls.__dict__.items():
            for handler_type in handlers:
                if hasattr(method, handler_type):
                    handlers[handler_type].append((getattr(method, handler_type), name))

        for handler_type in handlers:
            setattr(cls, handler_type, 
                    [handler[1] for handler in sorted(handlers[handler_type])])

    def _initialize(self):
        for method_name in self._initializer:
            getattr(self, method_name)()

    def _handle_event(self, event):
        for method_name in self._event_handler:
            getattr(self, method_name)(event)

    def _finalize(self):
        for method_name in self._finalizer:
            getattr(self, method_name)()

    def run(self):
        self._initialize()

        for event in range(10):
            self._handle_event(event)

        self._finalize()


class Recorder(Framework):

    @on_finalize(precedence=0)
    def save_to_db(self):
        print('save_to_db')


class TestFramework(Recorder):

    @on_initialize(precedence=0)
    def get_data(self):
        print('get_data')

    @on_initialize(precedence=1)
    def prepare_data(self):
        print('prepare_data')

    @on_event(precedence=0)
    def process_event(self, event):
        print('process_event', event)

    @on_finalize(precedence=1)
    def generate_report(self):
        print('generate_report')

if __name__ == '__main__':
    tf = TestFramework()
    tf.run()

结果：

> get_data 
> prepare_data 
> process_event 0 
> process_event 1 
> process_event 2
> process_event 3 
> process_event 4 
> process_event 5 
> process_event 6
> process_event 7 
> process_event 8 
> process_event 9 
> generate_report

Recorder 中的方法 save_to_db 不会在 TestFramework 中执行。我想我在__init_subclass__ 中遗漏了一些东西，我应该遍历每个子类。任何想法？非常感谢！

Answer 1

您为每个类设置一组新的处理程序，忽略任何基类的处理程序。

不要使用 handlers 字典中的空列表，而是查找现有列表并从这些列表开始：

def __init_subclass__(cls, *args, **kw):
    super().__init_subclass__(*args, **kw)
    handlers = dict(
        _initializer=getattr(cls, '_initializer', []),
        _event_handler=getattr(cls, '_event_handler', []),
        _finalizer=getattr(cls, '_finalizer', [])))
    # ...

然后您必须消除子类已覆盖的任何方法！

或者，不要只使用当前类命名空间（通过cls.__dict__），而是使用dir() 中可用的组合名称：

def __init_subclass__(cls, *args, **kw):
    super().__init_subclass__(*args, **kw)
    handlers = dict(_initializer=[], _event_handler=[], _finalizer=[])
    for name in dir(cls):
        method = getattr(cls, name)
        for handler_type in handlers:
            if hasattr(method, handler_type):
                handlers[handler_type].append((getattr(method, handler_type), name))