debasishg

// the ADT
sealed trait Account {
  def no: String
  def name: String
  def openingDate: Date
  def closeDate: Option[Date]
}

final case class CheckingAccount private[prop](no: String, name: String, openingDate: Date, closeDate: Option[Date]) 

debasishg

sealed trait Base
case class D1(...) extends Base
case class D2(...) extedns Base

// Have defined all instances of EncodeJson & DecodeJson for D1 and D2

// works in 6.0.x but does not compile in 6.1-M5 since DecodeResult is now invariant
implicit val decode: DecodeJson[Base] = DecodeJson { c =>
  (c --\ "storeDelete").as[D1]  |||
  (c --\ "indexState").as[D2]   |||

debasishg

trait AccountRepository { 
  def query(no: String): \/[NonEmptyList[String], Option[Account]]
  def store(a: Account): \/[NonEmptyList[String], Account]
  def query(openedOn: Date): \/[NonEmptyList[String], Seq[Account]]
  def all: \/[NonEmptyList[String], Seq[Account]]
}

/**
 * and an implementation for this trait 
**/

debasishg

trait Writes[T] {
  def writes(o: T): JsValue
}

trait Reads[T] {
  def reads(json: JsValue): T
}

trait Format[T] extends Writes[T] with Reads[T]

debasishg

Welcome to Scala version 2.11.5 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_65).
Type in expressions to have them evaluated.
Type :help for more information.

scala> import frdomain.ch3.repository._
import frdomain.ch3.repository._

scala> import reader._
import reader._

debasishg

/**
 * http://stackoverflow.com/questions/16015020/what-does-coalgebra-mean-in-the-context-of-programming
 **/
def op[T: Monoid](arg: \/[(T, T), T]): T = {
  val m = implicitly[Monoid[T]]
  arg match {
    case -\/((a, b)) => m.append(a, b)
    case \/-(a) => m.zero
  }
}

debasishg

val c1 = new PubSubClient("foo", r)
c1.start
val c2 = new PubSubClient("bar", t)
c2.start
val server = new PubSubServer
server.start

server ! Subscribe(c1, List("a", "b", "c"))
server ! Publish(c2, "a", "hello")
server ! Publish(c2, "c", "hi")

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object Sub {
  println("starting subscription service ..")
  val s = new Subscriber(new RedisClient("localhost", 6379))
  s.start
  s ! Register(callback) 

  def sub(channels: String*) = {
    s ! Subscribe(channels.toArray)
  }

debasishg

def callback(pubsub: PubSubMessage) = pubsub match {
  case S(channel, no) => println("subscribed to " + channel + " and count = " + no)
  case U(channel, no) => println("unsubscribed from " + channel + " and count = " + no)
  case M(channel, msg) => 
    msg match {
      // exit will unsubscribe from all channels and stop subscription service
      case "exit" => 
        println("unsubscribe all ..")
        r.unsubscribe

debasishg

1. Download redis from http://github.com/antirez/redis
2. build using "make"
3. Run server as ./redis-server