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core.messaging.composers.message_composer

MessageComposer Objects​

class MessageComposer(abc.ABC)

A class to collect all information necessary to create and emit a message.

__init__​

def __init__(origin_id: UnitID,
             message_bus: MessageBusProtocol,
             msg_type: type[MessageType],
             chain: Message | None = None,
             **kwargs)

Arguments:

  • origin_id - The component identifier of the origin of newly created messages.
  • message_bus - The global message bus to use.
  • msg_type - The message type.
  • chain - A message that acts as the predecessor of the new message. Used to keep the same trace for multiple messages.
  • **kwargs - Additional message parameters.

add_payload​

def add_payload(key: str, data: PayloadData) -> None

Adds a payload item to the message.

Arguments:

  • key - The item key.
  • data - The item data.

before​

def before(callback: BeforeDispatchCallback) -> typing.Self

Adds a callback that will be called immediately before the message is dispatched.

Arguments:

  • callback - The callback to add.

Returns:

This composer instance to allow call chaining.

emit​

def emit(target: Channel) -> None

Sends the built message through the message bus.

Arguments:

  • target - The target of the message.