ShowTypeClass.scala

final case class MyCaseClass(id: Int, name: String)

final case class MyOtherCaseClass(id: Int, name: String)


trait Show[-A]{
  def show(a: A): String
}

object Show {
  
  def apply[A](a: A)(implicit sh: Show[A]) = implicitly[Show[A]].show(a)
  
  implicit val intCanShow: Show[Int] =
    new Show[Int]{
      def show(int: Int): String = s"int $int"
    }
  
  implicit val strCanShow: Show[String] =
    new Show[String]{
      def show(str: String): String = s"a string $str"
    }
  
  implicit val myCaseClassCanShow: Show[MyCaseClass] =
    new Show[MyCaseClass]{
      def show(myCaseClass: MyCaseClass): String =
        Show(myCaseClass.id) + " " + Show(myCaseClass.name)
    }
  
  implicit def optCanShow[B : Show]: Show[Option[B]] =
    new Show[Option[B]]{
      def show(opt: Option[B]): String =
       opt match {
         case Some(x) => "Some " + Show(x)
         case None    => "None"
       }
    }
}

println(Show(223))
println(Show("hello"))
println(Show(Some(233)))
println(Show(Some("hello")))
println(Show(Some(MyCaseClass(1,"eric"))))


//println(Show(Some(200.94203)))  // <- will not compile

//println(Show(Some(MyOtherCaseClass(1,"eric")))) //<- will not compile