How to access and mutate private field in scala?

Question

I have something like:

class Address(private var street:String, private var city: String, private var postCode: String) extends Model

When I try to do:

address = new Address(....)
address.city = "changed"

I get compile error. So what is the solution? Note that the fields must remain private.

Also is there a shortcut syntax than having to repeat the keyword private when all fields in the class are private?

Answer 1

There seems to be a fundamental misunderstanding here. All fields in Scala are private. It's not just a default nor is it optional.

For example, let's say you have this:

class Address(var street: String)

The field where street is stored is private. Say you do this:

val x = new Address("Downing")
println(x.street)

This code does not directly access the private field for street. x.street is a getter method.

Say you do this:

x.street = "Boulevard"

This code does not directly modify the private field for street. x.street = is actually the method x.street_=, which is a setter method.

You can't directly access fields in Scala. Everything is done through getters and setters. In Scala, every field is private, every field has getters, and every var has setters.

Answer 2

You can define accessors and mutators like this:

class Address(private var _street: String, private var _city: String, private var _postCode: String){
  def street = _street
  def street_=(street: String) = _street = street

  def city = _city
  def city_=(city: String) = _city = city

  def postCode = _postCode
  def postCode_=(postCode: String) = _postCode = postCode
}

The need to rename the fields (which might clash with named parameters) and that the constructor ignores the mutator when instantiating the class is a known problem, but no efforts are currently made to improve the situation.