on

Register an event listener for state changes on this message. The handler is called each time a messaging.state event is received for this message, allowing you to react to intermediate states before the terminal state is reached.

Parameters

handler

Callable[[RelayEvent], None]Required

A function or coroutine that receives a RelayEvent on each state change. Both synchronous and async handlers are supported.

Returns

None

Example

import asyncio
from signalwire.relay import RelayClient
client = RelayClient(
    project="your-project-id",
    token="your-api-token",
    contexts=["default"],
)
async def track_state():
    async with client:
        message = await client.send_message(
            to_number="+15551234567",
            from_number="+15559876543",
            body="Order confirmed",
        )
        def on_state_change(event):
            print(f"Message {message.message_id} -> {message.state}")
        message.on(on_state_change)
        await message.wait()
asyncio.run(track_state())