Handlers and subscribers

• Handlers are functions that can be "subscribed" by other functions.
• Subscribers are functions that have "subscribed" to a handler.

Handlers can have multiple subscribers, and subscribers can bind to multiple handlers.

Subscribers

def __init__(self, loader):
    # Subscribe a function to desuko.bot.register_slash (the handler).
    # You should always provide a full import path. Relative ones
    # are not supported.
    loader.subscribe('desuko.bot.register_slash', self.sub)

def sub(self):
    print('I will be executed after desuko.bot.register_slash!')

Warning

Subscribers are stored in set. Thus, they don't have an execution order.

Handlers

handler_tutorial.py:

def __init__(self, loader):
    # loader.handler() returns a function that calls a provided one
    # and its subscribers.
    self.handler = loader.handler(self._inner_handler_func)
    loader.subscribe('handler_tutorial.handler', self.sub)

def _inner_handler_func(self):
    print('I will be executed first!')

def sub(self):
    print('I will be executed after self._inner_handler_func()!')

Execution order:

1. __init__()
2. handler_tutorial.handler()
3. self._inner_handler_func()
4. Subscribers of handler_tutorial.handler()

Asyncronious functions

Subscribers can be asynchronous only if their handler is also asynchronous.

def __init__(self, loader):
    self.handler = loader.handler(self._inner_handler_func)
    loader.subscribe('handler_tutorial.handler', self.sub)

def _inner_handler_func(self):
    print('I will be executed first!')

async def sub(self):
    print('I will not be executed at all!')

...will raise an exception.

def __init__(self, loader):
    self.handler = loader.handler(self._inner_handler_func, return_async=True)
    loader.subscribe('handler_tutorial.handler', self.sub)

async def _inner_handler_func(self):
    print('I will be executed first!')

async def sub(self):
    print('I will be executed after self._inner_handler_func()!')

...will execute normally.

Note

To work with asynchronous handlers, specify return_async=True when creating them.