Add the pipe pattern section (#23948)

akka-docs/src/test/scala/docs/future/FutureDocSpec.scala

@@ -7,8 +7,7 @@ package docs.future
 import language.postfixOps
 
 import akka.testkit._
-import akka.actor.{ Actor, Props }
-import akka.actor.Status
+import akka.actor.{ Actor, ActorRef, Props, Status }
 import akka.util.Timeout
 import scala.concurrent.duration._
 import java.lang.IllegalStateException
@@ -35,6 +34,95 @@ object FutureDocSpec {
         n += 2
     }
   }
+
+  //#pipe-to-usage
+  class ActorUsingPipeTo(target: ActorRef) extends Actor {
+    // akka.pattern.pipe needs to be imported
+    import akka.pattern.{ask, pipe}
+    // implicit ExecutionContext should be in scope
+    implicit val ec: ExecutionContext = context.dispatcher
+
+    def receive = {
+      val future = target ? "some message"
+      future pipeTo sender() // use the pipe pattern
+    }
+  }
+  //#pipe-to-usage
+
+  //#pipe-to-returned-data
+  case class UserData(data: String)
+  case class UserActivity(activity: String)
+  //#pipe-to-returned-data
+
+  //#pipe-to-user-data-actor
+  class UserDataActor extends Actor {
+    import UserDataActor._
+
+    //holds the user data internally
+    var internalData: UserData = UserData("initial data")
+
+    def receive = {
+      case Get ⇒
+        sender() ! internalData
+    }
+  }
+
+  object UserDataActor {
+    case object Get
+  }
+  //#pipe-to-user-data-actor
+
+  //#pipe-to-user-activity-actor
+  trait UserActivityRepository {
+    def queryHistoricalActivities(userId: String): Future[List[UserActivity]]
+  }
+
+  class UserActivityActor(val userId: String, repository: UserActivityRepository) extends Actor {
+    import akka.pattern.pipe
+    import UserActivityActor._
+    implicit val ec: ExecutionContext = context.dispatcher
+
+    def receive = {
+      case Get ⇒
+        // user's historical activities are retrieved
+        // via the separate repository
+        repository.queryHistoricalActivities(userId) pipeTo sender()
+    }
+  }
+
+  object UserActivityActor {
+    case object Get
+  }
+  //#pipe-to-user-activity-actor
+
+  //#pipe-to-proxy-actor
+  class UserProxyActor(
+    userData:       ActorRef,
+    userActivities: ActorRef
+  ) extends Actor {
+    import UserProxyActor._
+    import akka.pattern.{ ask, pipe }
+    implicit val ec: ExecutionContext = context.dispatcher
+
+    implicit val timeout = Timeout(5 seconds)
+
+    def receive = {
+      case GetUserData ⇒
+        (userData ? UserDataActor.Get) pipeTo sender()
+      case GetUserActivities ⇒
+        (userActivities ? UserActivityActor.Get) pipeTo sender()
+    }
+  }
+  //#pipe-to-proxy-actor
+
+  //#pipe-to-proxy-messages
+  object UserProxyActor {
+    sealed trait Message
+    case object GetUserData extends Message
+    case object GetUserActivities extends Message
+  }
+  //#pipe-to-proxy-messages
+
 }
 
 class FutureDocSpec extends AkkaSpec {
@@ -73,11 +161,6 @@ class FutureDocSpec extends AkkaSpec {
     val result = Await.result(future, timeout.duration).asInstanceOf[String]
     //#ask-blocking
 
-    //#pipe-to
-    import akka.pattern.pipe
-    future pipeTo actor
-    //#pipe-to
-
     result should be("HELLO")
   }