What does the word “Action” do in a Scala function definition using the Play framework?

Question

I am developing Play application and I\'ve just started with Scala. I see that there is this word Action after the equals sign in the function below and before curl

Answer 1

Its the Action being called on with an expression block as argument. (The apply method is used under the hood).

Action.apply({
  Ok("Hello world")
})

A simple example (from here) is as follows (look at comments in code):

case class Logging[A](action: Action[A]) extends Action[A] {

  def apply(request: Request[A]): Result = {// apply method which is called on expression
    Logger.info("Calling action")
    action(request) // action being called on further with the request provided to Logging Action
  }

  lazy val parser = action.parser
}

Now you can use it to wrap any other action value:

def index = Logging { // Expression argument starts
  Action { // Action argument (goes under request)
    Ok("Hello World")
  }
}

Also, the case you mentioned for def index = { is actually returning Unit like: def index: Unit = {.