Conventions

In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "Update the index template so that each <li> element has a button, clicking on which results in a delete request to the server."

A block of code is set as follows:

def running[T](app: Application)(block: => T): T = {
    synchronized {
      try {
        Play.start(app)
        block
      } finally {
        Play.stop()
      }
    }
  }

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

class WebSocketChannel(out: ActorRef)
  extends Actor with ActorLogging {

  val backend = Akka.system.actorOf(DBActor.props)
  def receive: Actor.Receive = {
    case jsRequest: JsValue =>
      backend ! convertJsonToMsg(jsRequest)
    case x:DBResponse =>
      out ! x.toJson
  }
}

Any command-line input or output is written as follows:

> run
[info] Compiling 1 Scala source to /AkkaActorDemo/target/scala-2.10/classes...
[info] Running com.demo.Main
?od u od woH ,olleH
ekops ew ecnis gnoL neeB
Sorry, didn't quite understand that I can only process a String.

New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "The form is not submitted when you click on Submit, and no errors are displayed using globalErrors."