A practical example of the Type class pattern in Scala

typeclassExample.scala

//Type class pattern example in Scala, to achieve ad hoc polymorphism

case class Picture(name: String, uri: String)

case class Attachment(name: String, uri: String, visible: Boolean)

trait JsonSerializer[T]{
  def toJson(in: T): String
}

object JsonSerializer{
  def jsonOf[T](in: T)(implicit jsonSerializer: JsonSerializer[T]): String =
    jsonSerializer.toJson(in)
   
  // Or this more succinct version
  //
  //def jsonOf[T: JsonSerializer](in: T): String = 
  //  implicitly[JsonSerializer[T]].toJson(in)
  
  implicit val pictureJsonSerializer = new JsonSerializer[Picture]{
    override def toJson(in: Picture): String = s"picture ${in.name}"
  }  
  
  implicit val attachmentJsonSerializer = new JsonSerializer[Attachment]{
    override def toJson(in: Attachment): String = s"attachment ${in.name}"
  }
  
}

import JsonSerializer._

println(jsonOf(new Picture("mypic", "mypicurl")))

println(jsonOf(new Attachment("myattachment", "myurl", false)))