Actix - running actors

help
1

Hello.
I would like to run actors based on the configuration.
In the first step I want to create an actor. Then start it if the name is in the list (cfg).
How to get sender address in handler ?

use actix::*;
use std::collections::HashMap;

struct MyActor
{
    val: usize,
}

impl MyActor
{
    pub fn new() -> Self { return MyActor{ val: 0 }; }
}

impl Actor for MyActor
{
    type Context = Context<Self>;
}

#[derive(Debug, Clone)]
pub struct PushData<T> {
    pub value: T,
}

impl<T: 'static> Message for PushData<T>
{
    type Result = T;
}

impl Handler<PushData> for MyActor
{
    type Result = ();

    fn handle(&mut self, msg: PushData, ctx: &mut Self::Context) -> Self::Result
    {
          // ...any code
    }
}

fn main()
{
    //load actors
    let mut actors = HashMap::new();
    actors.insert("MyActor1", MyActor::new());

    //config
    let mut cfg = Vec::new();
    cfg.push("MyActor1");
    cfg.push("MyActor2");
    cfg.push("MyActorX");

    for c in cfg
    {
        System::run(move || {
            let addr = actors[c].start();
        });
    }
}

Errors:

error[E0507]: cannot move out of index of `std::collections::HashMap<&str, MyActor>`
  --> src/main.rs:45:24
   |
45 |             let addr = actors[c].start();
   |                        ^^^^^^^^^ move occurs because value has type `MyActor`, which does not implement the `Copy` trait

   |
32 |     let mut actors = HashMap::new();
   |         ---------- move occurs because `actors` has type `std::collections::HashMap<&str, MyActor>`, which does not implement the `Copy` trait
...
44 |         System::run(move || {
   |                     ^^^^^^^ value moved into closure here, in previous iteration of loop
45 |             let addr = actors[c].start();
   |                        ------ use occurs due to use in closure
2

You have to take ownership of the actor. The self() method destroys the actor, so it cannot still be in the hash map.

for c in cfg
{
    let actor = actors.remove(c).expect("No such actor");
    System::run(move || {
        let addr = actor.start();
    });
}
1 Like
3

@alice, thx for reply.
One more question... How to get sender address in handler ?

4

What does your handler look like? How is it called? If you show a more complete example, it will be easier to help.

5 
impl Handler<PushData> for MyActor
{
    type Result = ();

    fn handle(&mut self, msg: PushData, ctx: &mut Self::Context) -> Self::Result
    {
          // ...any code
    }
}
6

Oh I see what you're asking. I'm not super familiar with actix, but I don't think there's a direct way to access that. I think if you want the sender address, I would include it in the message. This is a common pattern in multi threaded code to send an address or a channel with a message to enable responding to a message.

7

In my solution I have an address in the message - PushData.
But I expected to get the address from the context variable - ctx: &mut Self::Context.

8

The context can get you the address of the current actor. Make sure you have use actix::AsyncContext at the top of the file, then I believe you can use ctx.address() to get the address of the current actor.

actix::AsyncContext

9

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