How can an actor send an event of a type which is different from the 'type Event'?

[jano7]

For example an actor of a drone app which is responsible for converting UDP packets (type Event = UDP) from a receiver to a command (which is an enum of UP/DOWN/RIGHT/LEFT...).

[ddrcode]

Thank you for the question, @jano7

The supervisor is defined as Supervisor<E: Event, T: Topic<E>>, so all actors registered with one supervisor must be sending events of the same type. Normally event and topic types are enums, so if you need a new type, you add a new option to the enum. But if you truly need to support different event types, you would need multiple supervisors and some way of synchronizing them (Maiko doesn't provide such such mechanism yet).

If I understand your case properly, you translate from one protocol (UDP) to another (Tokio channels in Maiko). That's completely doable - you simply need a dedicated actor that translates UDP packets into internal events (you call them commands). It would look as such (pseudocode):

pub struct UDPReceiver {
    ctx: maiko::Context<Command>,
    sock: UdpSocket
}

impl Actor for UDPReceiver {
   async fn step(&mut self) -> maiko::Result<StepAction> {
        let mut buf = [0; 1024];
        let (len, addr) = self.sock.recv_from(&mut buf).await?; // read from udp
        if let Ok(event) = Command::try_from((&buf, len)) { // try to convert the udp to local event (Command)
             self.ctx.send(event).await; // send the command
        }
        Ok(StepAction::Yield) // or StepAction::Continue
   }
}

#[derive(Event, Label)]
pub enum Command {
   Left, Right, Up, Down
}

impl TryFrom<(&[u8], len)> for Command {
   // do the conversion
}

In the example the actor is pure event producer - it listens to UDP packets and sends events. It even doesn't listen to other Maiko events. If it needed to - you just add handle_event method implementation and then it will be both - event producer and consumer.

Hope that makes sense. If you want to clarify it further i am happy to help.

On real life example similar (somehow) to your case - in my project Charon I have an actor that listens to Linux system events (evdev) and translates them to Maiko events. Same idea, just different protocol. See it here: KeyScanner