dci.scala

//database model
case class Account(id: Identifier, owner: User, var balance: Money)

object AccountRepository {
  def lookUp(id: Int):Account = Account("id1", "notyy", 100.0) //just an example
}

//DCI model
class AccountHolder(val account: Account) //adaptor

trait TransferSource { this: AccountHolder =>
  def transferOut(amount: Money) = this.account.balance -= amount
}

trait TransferTarget { this: AccountHolder =>
  def transferIn(amount: Money) = this.account.balance += amount
}

object TransferService {
  def transfer(srcAccount: TransferSource, targetAccount: TransferTarget, amount: Money):Unit = {
    if(!canTransfer()) throw new IllegalArgumentException("can't transfer")

    srcAccount.transferOut(amount)
    targetAccount.transferIn(amount)
  }

  def canTransfer() = true
}

//context
val transferSource = new AccountHolder(AccountRepository.lookUp(1)) with TransferSource
val transferTarget = new AccountHolder(AccountRepository.lookUp(2)) with TransferTarget

TransferService.transfer(transferSource, transferTarget, 200.0)