11.3. Event Programming¶
11.3.1. Rationale¶
EN: Callback Design
PL:
11.3.2. Metaclass¶
>>> class EventListener(type):
... listeners: dict[str, list[callable]] = {}
...
... @classmethod
... def register(cls, *clsnames):
... def wrapper(func):
... for clsname in clsnames:
... if clsname not in cls.listeners:
... cls.listeners[clsname] = []
... cls.listeners[clsname] += [func]
... return wrapper
...
... def __new__(mcs, classname, bases, attrs):
... for listener in mcs.listeners.get(classname, []):
... listener.__call__(classname, bases, attrs)
... return type(classname, bases, attrs)
>>>
>>>
>>> @EventListener.register('Astronaut')
... def hello_class(clsname, bases, attrs):
... print(f'\n\nHello new class {clsname}\n')
>>>
>>>
>>> @EventListener.register('Astronaut', 'Person')
... def print_name(clsname, bases, attrs):
... print('\nNew class created')
... print('Classname:', clsname)
... print('Bases:', bases)
... print('Attrs:', attrs)
>>>
>>>
>>> class Person(metaclass=EventListener):
... pass
New class created
Classname: Person
Bases: ()
Attrs: {'__module__': 'builtins', '__qualname__': 'Person'}
>>>
>>> class Astronaut(Person, metaclass=EventListener):
... pass
Hello new class Astronaut
New class created
Classname: Astronaut
Bases: (<class 'Person'>,)
Attrs: {'__module__': 'builtins', '__qualname__': 'Astronaut'}
11.3.3. Implementation¶
class event:
__slots__ = ('__subscribers', )
def __init__(self):
self.__subscribers = set()
def call(self, *args, **kwargs):
for subscriber in self.__subscribers:
subscriber(*args, **kwargs)
__call__ = call
def register(self, function):
self.__subscribers.add(function)
return self
__add__ = __iadd__ = register
def unregister(self, function):
self.__subscribers.remove(function)
return self
__sub__ = __isub__ = unregister
class EventManager:
@staticmethod
def register(name):
if not hasattr(EventManager, name):
setattr(EventManager, name, event())
return getattr(EventManager, name).register
Use Case:
@EventManager.register('on_foo')
def foo(*args, **kwargs):
print('Args: ' + str(args), 'Kwargs: ' + str(kwargs))
def call_on_foo():
EventManager.on_foo()
EventManager.on_foo(1, 2, 3)
EventManager.on_foo(a=1, b=2, c=3)
EventManager.on_foo(1, 2, 3, a=1, b=2, c=3)
@EventManager.register('on_bar')
def bar():
call_on_foo()
EventManager.on_bar()
Use:
EventManager.on_bar + funkcja
EventManager.on_bar += funkcja