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core.messaging.composers.message_builder

MessageBuilder Objects​

class MessageBuilder()

A helper class to easily build and emit new messages.

This class stores a reference to the global message bus and offers methods to easily create new messages and send them through the bus.

__init__​

def __init__(origin_id: UnitID, message_bus: MessageBusProtocol)

Arguments:

  • origin_id - The component identifier of the origin of newly created messages.
  • message_bus - The global message bus to use.

build_command​

def build_command(cmd_type: type[CommandType],
                  chain: Message | None = None,
                  **kwargs) -> CommandComposer

Builds a new command.

Arguments:

  • cmd_type - The command type (i.e., a subclass of Command).
  • 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.

Returns:

A message composer to further build and finally emit the message.

Raises:

  • RuntimeError - cmd_type is not a subclass of Command.

build_command_reply​

def build_command_reply(reply_type: type[CommandReplyType],
                        command: CommandType,
                        success: bool = True,
                        message: str = "",
                        **kwargs) -> CommandReplyComposer

Builds a new command reply.

Arguments:

  • reply_type - The command reply type (i.e., a subclass of CommandReply).
  • command - The Command this reply is based on.
  • success - Whether the command succeeded or not (how this is interpreted depends on the command).
  • message - Additional message to include in the reply.
  • **kwargs - Additional message parameters.

Returns:

A message composer to further build and finally emit the message.

Raises:

  • RuntimeError - reply_type is not a subclass of CommandReply.

build_event​

def build_event(event_type: type[Event],
                chain: Message | None = None,
                **kwargs) -> EventComposer

Builds a new event.

Arguments:

  • event_type - The event type (i.e., a subclass of Event).
  • 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.

Returns:

A message composer to further build and finally emit the message.

Raises:

  • RuntimeError - event_type is not a subclass of Event.

get_message_count​

def get_message_count(msg_type: MessageType) -> int

Gets how many messages of specific message types have been created.

The message builder keeps track of how many messages of the three major types Command, CommandReply and Event have been created.

Arguments:

  • msg_type - The message type to get the count of. Must be either Command, CommandReply or Event.

Returns:

The number of messages already built of the specified type.