Message handlers

`depeche_db.MessageHandlerRegisterProtocol`

Bases: Protocol, Generic[E]

Message handler register protocol is used by runners to find handlers for messages.

Implemented by

MessageHandlerRegister
MessageHandler

`get_all_handlers()`

Returns all registered handlers.

`get_handler(message_type)`

Returns a handler for a given message type.

`depeche_db.MessageHandlerRegister()`

Bases: Generic[E]

Message handler register is a registry of message handlers.

Typical usage:

handlers = MessageHandlerRegister()

@handlers.register
def handle_message(message: MyMessage):
    ...

@handlers.register
def handle_other_message(message: StoredMessage[MyOtherMessage]):
    ...

Implements: MessageHandlerRegisterProtocol

`register(handler)`

Registers a handler for a given message type.

The handler must have at least one parameter. The first parameter must be of a message type. E being your message type, the parameter can be of type E, SubscriptionMessage[E] or StoredMessage[E]. When a handler is called, the message will be passed in the requested type.

Multiple handlers can be registered for non-overlapping types of messages. Overlaps will cause a ValueError.

Parameters:

Name	Type	Description	Default
`handler`	`H`	A handler function.	required

Returns:

Type	Description
`H`	The unaltered handler function.

`register_manual(handler, handled_type, requires_middleware=False)`

Registers a handler for a given message type.

The handler must have at least one parameter. The first parameter must be of a message type.

Same overlap rules apply to this method as to the register method.

If the handler takes more than one parameter, you must set the requires_middleware parameter to True!

Parameters:

Name	Type	Description	Default
`handler`	`H`	A handler function.	required
`handled_type`	`Type`	The type of message to handle.	required
`requires_middleware`	`bool`	Whether the handler requires middleware.	`False`

`depeche_db.MessageHandler()`

Bases: Generic[E]

Message handler is a base class for message handlers.

This is basically a class-based version of the MessageHandlerRegister.

Typical usage (equivalent to the example in MessageHandlerRegister):

class MyMessageHandler(MessageHandler):
    @MessageHandler.register
    def handle_message(self, message: MyMessage):
        ...

    @MessageHandler.register
    def handle_other_message(self, message: StoredMessage[MyOtherMessage]):
        ...

Implements: MessageHandlerRegisterProtocol