Function ask 

pub fn ask<Msg, Ctx, R, T>(ctx: &Ctx, receiver: &T, msg: Msg) -> RemoteHandle<R>
where
    Msg: Message,
    R: Message,
    Ctx: TmpActorRefFactory + Run,
    T: Tell<Msg>,

Convenience fuction to send and receive a message from an actor

This function sends a message msg to the provided actor receiver and returns a Future which will be completed when receiver replies by sending a message to the sender. The sender is a temporary actor that fulfills the Future upon receiving the reply.

futures::future::RemoteHandle is the future returned and the task is executed on the provided executor ctx.

This pattern is especially useful for interacting with actors from outside of the actor system, such as sending data from HTTP request to an actor and returning a future to the HTTP response, or using await.

Examples

#[derive(Default)]
struct Reply;

impl Actor for Reply {
   type Msg = String;

   fn recv(&mut self,
                ctx: &Context<Self::Msg>,
                msg: Self::Msg,
                sender: Sender) {
        // reply to the temporary ask actor
        sender.as_ref().unwrap().try_tell(
            format!("Hello {}", msg), None
        ).unwrap();
    }
}

// set up the actor system
let sys = ActorSystem::new().unwrap();

// create instance of Reply actor
let actor = sys.actor_of::<Reply>("reply").unwrap();

// ask the actor
let msg = "Will Riker".to_string();
let r: RemoteHandle<String> = ask(&sys, &actor, msg);

assert_eq!(block_on(r), "Hello Will Riker".to_string());