Added patterns for initialization for Scala #2297

(cherry-picked from e2aa3b5)

akka-docs/rst/scala/code/docs/actor/InitializationDocSpec.scala

@@ -0,0 +1,74 @@
+/**
+ * Copyright (C) 2009-2013 Typesafe Inc. <http://www.typesafe.com>
+ */
+package docs.actor
+
+import akka.actor.{ Props, Actor }
+import akka.testkit.{ ImplicitSender, AkkaSpec }
+
+object InitializationDocSpec {
+
+  class PreStartInitExample extends Actor {
+    override def receive = {
+      case _ ⇒ // Ignore
+    }
+
+    //#preStartInit
+    override def preStart(): Unit = {
+      // Initialize children here
+    }
+
+    // Overriding postRestart to disable the call to preStart()
+    // after restarts
+    override def postRestart(reason: Throwable): Unit = ()
+
+    // The default implementation of preRestart() stops all the children
+    // of the actor. To opt-out from stopping the children, we
+    // have to override preRestart()
+    override def preRestart(reason: Throwable, message: Option[Any]): Unit = {
+      // Keep the call to postStop(), but no stopping of children
+      postStop()
+    }
+    //#preStartInit
+  }
+
+  class MessageInitExample extends Actor {
+    //#messageInit
+    var initializeMe: Option[String] = None
+
+    override def receive = {
+      case "init" ⇒
+        initializeMe = Some("Up and running")
+        context.become(initialized, discardOld = true)
+
+    }
+
+    def initialized: Receive = {
+      case "U OK?" ⇒ initializeMe foreach { sender ! _ }
+    }
+    //#messageInit
+
+  }
+}
+
+class InitializationDocSpec extends AkkaSpec with ImplicitSender {
+  import InitializationDocSpec._
+
+  "Message based initialization example" must {
+
+    "work correctly" in {
+      val example = system.actorOf(Props[MessageInitExample], "messageInitExample")
+      val probe = "U OK?"
+
+      example ! probe
+      expectNoMsg()
+
+      example ! "init"
+      example ! probe
+      expectMsg("Up and running")
+
+    }
+
+  }
+
+}