how to store object state before and after setting attribute values

Question

i have a class Demo i want to save object value before setting attribute value here is my code

case class Demo (var abc:String)

      val d =Demo("bob")
      var oldDemo=d
      d.abc="joe"

      println("old name is "+oldDemo.abc +" the new name is "+d.abc)

the output printed on the console is

old name is joe the new name is joe

i want to store object value before setting d.abc="joe" so that i can get bob when i do oldDemo.abc please guide me where i am going wrong and what is the right way to achieve my goal .and i apologize if i am doing something stupid

Answer 1

You can use copy() on a case class.

val d1 = Demo("abc")
val d2 = d1.copy()
d1.abc = "def"

// d2 : Demo = Demo(abc)
// d1 : Demo = Demo(def)

A more Scala idiomatic way would be to use immutable case classes:

case class Person(name: String, age: Int)
val bob = Person("Bob", 30)
val joe = bob.copy(name="Joe")

// bob : Person = Person(Bob,30)
// joe : Person = Person(Joe,30)