Non Breaking Option

non-breaking-option.scala

import scalaz.Monad

import scalaz._, Scalaz._

object OptionTest {

  case class User(name: String, image: String)


  // Gets a user, optionally
  def getUserOp: Option[User] = Some(User("Paul", "paul.jpg"))
  
  // later, refactor so that we get a user always!
  def getUserExactly: Id[User] = User("Paul", "paul.jpg")

  // can only be used with Option[User], so this usage would break when we refactor getUserExactly
  def extractImage(userOp: Option[User]): Option[String] =
    userOp.map(_.image)

  // can be used for _any_ F, such that F can be treated as a Functor
  // (Option and Identity can be treated as such!)
  def extractImageNonBreaky[F[_]: Functor](userOp: F[User]): F[String] =
    Functor[F].map(userOp)(_.image)
  

  def main(args: Array[String]): Unit = {

    println(extractImage(getUserOp))
    // println(extractImage(getUserExactly))  <- this doesn't compile

    println(extractImageNonBreaky(getUserOp))
    println(extractImageNonBreaky(getUserExactly))
  }

}