functional typeclasses and object oriented typeclasses

gistfile1.scala

// functional typeclass pattern
// using type traits and implicit parameters

case class Person(name: String, age: Int)
case class Restaurant(name: String, location: String)

// Typeclass
trait Serializable[T] {
  def ser(t: T): String
}

// Companion to Typeclass that contains default implementation of typeclasses
// for various types
object Serializable {
  @inline def apply[T](implicit ev: Serializable[T]) = ev
  
  implicit object PersonIsSerializable extends Serializable[Person] {
    override def ser(p: Person) = p.toString
  }
  
  implicit object RestaurantIsSerializable extends Serializable[Restaurant] {
    override def ser(r: Restaurant) = r.toString
  }
  
  implicit def listToSerializable[T] = new Serializable[List[T]] {
    override def ser(l: List[T]) = l.mkString(", ") 
  }
  
  implicit def tuple2ToSerializable[T, U](implicit t: Serializable[T], u: Serializable[U]) = new Serializable[(T, U)] {
    override def ser(tuple: (T, U)) = "(" + t.ser(tuple._1) + ", " + u.ser(tuple._2) + ")"
  }
}

// A method with implicit parameter (or context bound) where typeclass is used
def serialize[T](t: T)(implicit ev: Serializable[T]): String = ev.ser(t)

// or, context bound syntax
// def serialize[T : Serializable](t: T): String = implicitly[Serializable[T]].ser(t)

serialize(Person("manju", 31)) // Person(manju,31)

serialize(Restaurant("bar tartine", "san francisco")) // Restaurant(bar tartine,san francisco)

serialize(List(1,2,3)) // 1, 2, 3

// object-oriented typeclass pattern
// using type traits, implicit parameters and implicit conversion

implicit def addSerialize[T](t: T)(implicit ev: Serializable[T]) = new { def serialize = ev.ser(t) }

// Or,
// implicit class SerializableOps[T](val t: T) extends AnyVal {
//   def serialize(implicit ev: Serializable[T]) = ev.ser(t)
// }
// Or,
// implicit class SerializableOps[T : Serializable](t: T) {
//   def serialize = implicitly[Serializable[T]].ser(t)
// }

Person("manju", 31).serialize // Person(manju,31)

(Person("manju", 31), List(1,2,3)).serialize // (Person(manju,31), 1, 2, 3)