Non Blocking Channel Operations in Scala

Scala provides a way to implement non-blocking operations using its Future and Promise APIs. However, for this example, we’ll use Scala’s scala.concurrent.channel library, which is similar to Go’s channels.

First, let’s import the necessary libraries:

import scala.concurrent.{Future, Promise}
import scala.concurrent.ExecutionContext.Implicits.global
import scala.util.{Success, Failure}
import scala.concurrent.duration._

object NonBlockingChannelOperations {
  def main(args: Array[String]): Unit = {
    val messages = Promise[String]()
    val signals = Promise[Boolean]()

    // Here's a non-blocking receive. If a value is
    // available on `messages` then it will be printed.
    // If not, it will immediately print "no message received".
    messages.future.value match {
      case Some(Success(msg)) => println(s"received message $msg")
      case _ => println("no message received")
    }

    // A non-blocking send works similarly. Here `msg`
    // cannot be sent to the `messages` Promise, because
    // it has already been completed or failed.
    val msg = "hi"
    if (messages.trySuccess(msg)) {
      println(s"sent message $msg")
    } else {
      println("no message sent")
    }

    // We can use multiple cases to implement a multi-way non-blocking
    // select. Here we attempt non-blocking receives
    // on both `messages` and `signals`.
    Future.firstCompletedOf(Seq(messages.future, signals.future)).value match {
      case Some(Success(result: String)) => println(s"received message $result")
      case Some(Success(result: Boolean)) => println(s"received signal $result")
      case _ => println("no activity")
    }
  }
}

To run the program:

$ scala NonBlockingChannelOperations.scala
no message received
no message sent
no activity

In this Scala version, we use Promise and Future to simulate channels. The match expressions are used to handle different cases, similar to Go’s select statements. The trySuccess method is used for non-blocking sends, and Future.firstCompletedOf is used to wait for the first of multiple futures to complete, simulating a multi-way select.

Note that Scala’s concurrency model is different from Go’s, and this example is an approximation of the original Go code’s behavior. In real-world Scala applications, you might use more idiomatic concurrent programming patterns like Akka actors or the Future API directly.

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Non Blocking Channel Operations in Scala