justinhj

case class AccountState(balance: Int, accountHolder: LastOption[String])

object AccountState {

    implicit def accountStateShow[A] = new Show[AccountState] {
        def show(a: AccountState): String = {
            show"Balance: ${a.balance}\nAccount holder: ${a.accountHolder}"
        }
    }
    implicit val accountMonoid = new Monoid[AccountState] {

justinhj

sealed trait BankAccountCommand
case class DepositCmd(time: Instant, amount: Int) extends BankAccountCommand
case class PurchaseCmd(time: Instant, amount: Int) extends BankAccountCommand
case class AssignAccountHolderCmd(time: Instant, accountHolder: String) extends BankAccountCommand

sealed trait BankAccountEvent
case class DepositEvt(time: Instant, amount: Int) extends BankAccountEvent
case class PurchaseEvt(time: Instant, amount: Int) extends BankAccountEvent
case class AssignAccountHolderEvt(time: Instant, accountHolder: String) extends BankAccountEvent

justinhj

trait PersistentEntity[IDType, T <: PersistentEntity[IDType, T]] {
    type Command
    type Event
    type State

    def id: IDType
    def state : State

    def processCommand(command: Command) : List[Event]
    def processEvent(event: Event) : T

justinhj

                  /*\
                 {\o/}
                  /_\
                 \*|*/
                ///|\\\
               ////|\\\\
              /////|\\\\\
             object MerryX
            {def main(santa
           : Array[String]){

justinhj

.onCommand[AssignAccountHolderCmd, Done]{
  case (AssignAccountHolderCmd(time, accountHolder), ctx, state) =>
    ctx.thenPersist(AssignAccountHolderEvt(time, accountHolder)){
      _ =>
        ctx.reply(Done)
    }
}

justinhj

Foldable[List].fold(List(1,2,3)) 
// res1: Int = 6

Foldable[List].fold(List("1","2","3")) 
// res2: String = "123"

// Or you can use the combineAll function

List(1,2,3).combineAll 
// res3: Int = 6

justinhj

import cats.Monoid

Monoid[Int].empty |+| 10 
// res1: Int = 10

10 |+| Monoid[Int].empty 
// res2: Int = 10

justinhj

trait Monoid[A] extends Semigroup[A] {
    def empty: A
}

justinhj

import cats.Foldable

// Combining a list with a foldLeft

Foldable[List].foldLeft(List(1,2,3), 0){_ |+| _} 
// res1: Int = 6

// Combining a list of string with a foldLeft

Foldable[List].foldLeft(List("1","2","3"), "")(_ |+| _) 

justinhj

import cats.Semigroup
import cats.implicits._

// Combining strings

"Semigroups".combine(" ".combine("combine".combine(" ".combine("things")))) 
// res1: String = "Semigroups combine things

// Which is hard to read so Cats provides convenient infix syntax