Question

Give me some help, I just cannot solve this problem.
How do I ensure that constraints on getter methods are always respected?
My classes have this form:

abstract class Element {
  var name: String
  var description: String
}

class Component (var name: String, var description: String) extends Element

For the purpose of my project I need to use var.
I want to put constraints on the field name that must always be respected.
Both when I create an instance of Component as follows:

val C1 = new Component ("C1 Component", "Description of C1")

Both when I change the value:

C1.name = "new value"

If I create the classes in this way:

abstract class Element {
  protected var _name : String
  // Getter
  final def name = _name
  // Setter
  final def name_= (value:String):Unit =
    if (value.size < 5) println ("ERROR: Bad Value")
    else _name = value

  var description: String
}

class Component (protected var _name : String, var description: String) extends Element

In the main method, because I do not have control here:

val C1 = new Component ("C1", "Description of C1")

But only later, when I change the value:

C1.name = "comp"

I want my getter to always be respected.
How do I do this?

Answer 1

class Component (_name : String, var description: String) extends Element {
  this.name = _name
}

Also, make var _name private, so subclasses can’t set it without using the setter.