Akka/Scala example source code file (AgentDocSpec.scala)

This example Akka source code file (AgentDocSpec.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Akka and Scala source code examples by using tags.

All credit for the original source code belongs to akka.io; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Akka tags/keywords

agent, agentdocspec, akka, akkaspec, any, boolean, concurrent, duration, future, int, just, test, testing, time

The AgentDocSpec.scala Akka example source code

/**
 * Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
 */
package docs.agent

import language.postfixOps

import akka.agent.Agent
import scala.concurrent.duration._
import scala.concurrent.{ Await, ExecutionContext }
import akka.testkit._
import scala.concurrent.Future

class AgentDocSpec extends AkkaSpec {
  "create" in {
    //#create
    import scala.concurrent.ExecutionContext.Implicits.global
    import akka.agent.Agent
    val agent = Agent(5)
    //#create
  }

  "read value" in {
    import scala.concurrent.ExecutionContext.Implicits.global
    val agent = Agent(0)

    {
      //#read-apply
      val result = agent()
      //#read-apply
      result should be(0)
    }
    {
      //#read-get
      val result = agent.get
      //#read-get
      result should be(0)
    }

    {
      //#read-future
      val future = agent.future
      //#read-future
      Await.result(future, 5 seconds) should be(0)
    }
  }

  "send and sendOff" in {
    val agent = Agent(0)(ExecutionContext.global)
    //#send
    // send a value, enqueues this change
    // of the value of the Agent
    agent send 7

    // send a function, enqueues this change
    // to the value of the Agent
    agent send (_ + 1)
    agent send (_ * 2)
    //#send

    def longRunningOrBlockingFunction = (i: Int) => i * 1 // Just for the example code
    def someExecutionContext() = scala.concurrent.ExecutionContext.Implicits.global // Just for the example code
    //#send-off
    // the ExecutionContext you want to run the function on
    implicit val ec = someExecutionContext()
    // sendOff a function
    agent sendOff longRunningOrBlockingFunction
    //#send-off

    Await.result(agent.future, 5 seconds) should be(16)
  }

  "alter and alterOff" in {
    val agent = Agent(0)(ExecutionContext.global)
    //#alter
    // alter a value
    val f1: Future[Int] = agent alter 7

    // alter a function
    val f2: Future[Int] = agent alter (_ + 1)
    val f3: Future[Int] = agent alter (_ * 2)
    //#alter

    def longRunningOrBlockingFunction = (i: Int) => i * 1 // Just for the example code
    def someExecutionContext() = ExecutionContext.global // Just for the example code

    //#alter-off
    // the ExecutionContext you want to run the function on
    implicit val ec = someExecutionContext()
    // alterOff a function
    val f4: Future[Int] = agent alterOff longRunningOrBlockingFunction
    //#alter-off

    Await.result(f4, 5 seconds) should be(16)
  }

  "transfer example" in {
    //#transfer-example
    import scala.concurrent.ExecutionContext.Implicits.global
    import akka.agent.Agent
    import scala.concurrent.duration._
    import scala.concurrent.stm._

    def transfer(from: Agent[Int], to: Agent[Int], amount: Int): Boolean = {
      atomic { txn =>
        if (from.get < amount) false
        else {
          from send (_ - amount)
          to send (_ + amount)
          true
        }
      }
    }

    val from = Agent(100)
    val to = Agent(20)
    val ok = transfer(from, to, 50)

    val fromValue = from.future // -> 50
    val toValue = to.future // -> 70
    //#transfer-example

    Await.result(fromValue, 5 seconds) should be(50)
    Await.result(toValue, 5 seconds) should be(70)
    ok should be(true)
  }

  "monadic example" in {
    def println(a: Any) = ()
    //#monadic-example
    import scala.concurrent.ExecutionContext.Implicits.global
    val agent1 = Agent(3)
    val agent2 = Agent(5)

    // uses foreach
    for (value <- agent1)
      println(value)

    // uses map
    val agent3 = for (value <- agent1) yield value + 1

    // or using map directly
    val agent4 = agent1 map (_ + 1)

    // uses flatMap
    val agent5 = for {
      value1 <- agent1
      value2 <- agent2
    } yield value1 + value2
    //#monadic-example

    agent3() should be(4)
    agent4() should be(4)
    agent5() should be(8)
  }
}