1    package scaladci 
2    package examples.MoneyTransfer 
3    import scala.language.reflectiveCalls 
4     
5    case class LedgerEntry(message: String, amount: Int) 
6     
7    case class Account(account: String, initialLedgers: List[LedgerEntry]) { 
8      private val ledgers = new { 
9        var ledgerList = initialLedgers 
10       def addEntry(message: String, amount: Int) { ledgerList = ledgerList :+ new LedgerEntry(message, amount) } 
11       def getBalance = ledgerList.foldLeft(0)(_ + _.amount) 
12     } 
13    
14     def balance = ledgers.getBalance 
15     def increaseBalance(amount: Int) { ledgers.addEntry("depositing", amount) } 
16     def decreaseBalance(amount: Int) { ledgers.addEntry("withdrawing", -amount) } 
17   } 
18    
19   class MoneyTransfer(src: Account, dest: Account, amount: Int) extends Context { 
20     private val source      = src.as[Source] 
21     private val destination = dest.as[Destination] 
22    
23     def transfer() { 
24       source.transfer 
25     } 
26    
27     private trait Source {self: Account => 
28       def withdraw() { 
29         decreaseBalance(amount) 
30       } 
31       def transfer() { 
32         println("Source balance is: " + balance) 
33         println("Destination balance is: " + destination.balance) 
34         destination.deposit() 
35         withdraw() 
36         println("Source balance is now: " + balance) 
37         println("Destination balance is now: " + destination.balance) 
38       } 
39     } 
40    
41     private trait Destination {self: Account => 
42       def deposit() { 
43         increaseBalance(amount) 
44       } 
45     } 
46   } 
47    
48   object MoneyTransferMarvinTest extends App { 
49     val source      = Account("salary", List(LedgerEntry("start", 0), LedgerEntry("first deposit", 1000))) 
50     val destination = Account("budget", List()) 
51     val context     = new MoneyTransfer(source, destination, 245) 
52     context.transfer() 
53   } 
54    
55   /* prints: 
56    
57   Source balance is: 1000 
58   Destination balance is: 0 
59   Source balance is now: 755 
60   Destination balance is now: 245 
61    
62   */