Case Classes and Pattern Matching

Copy and Update

Make a changed copy without mutating the original.

Copy and Update

CopyUpdate.scala 
case class Account(owner: String, balance: Int)

object Main {
  def main(args: Array[String]): Unit = {
    val deposit = 
    val base = Account("Ann", 100)
    val balance = base.balance + deposit
    val updated = base.copy(balance = balance)

    println("owner=" + updated.owner)
    println("oldBalance=" + base.balance)
    println("newBalance=" + updated.balance)
  }
}

case class Account(owner: String, balance: Int)

object Main {
  def main(args: Array[String]): Unit = {
    val deposit = 
    val base = Account("Ann", 100)
    val balance = base.balance + deposit
    val updated = base.copy(balance = balance)

    println("owner=" + updated.owner)
    println("oldBalance=" + base.balance)
    println("newBalance=" + updated.balance)
  }
}

case class Account(owner: String, balance: Int)

object Main {
  def main(args: Array[String]): Unit = {
    val deposit = 
    val base = Account("Ann", 100)
    val balance = base.balance + deposit
    val updated = base.copy(balance = balance)

    println("owner=" + updated.owner)
    println("oldBalance=" + base.balance)
    println("newBalance=" + updated.balance)
  }
}
copy-update The generated `copy` method returns a new case class instance with selected fields replaced. The original stays unchanged, which keeps state immutable.