有一个抽象类定义了带有默认值的主构造函数变量，我们如何从子类中设置该不可变值

Question

Given an abstract class:

abstract class SuperClass(val someVal: String = "defaultValue") : SomeSuperClass 

I want the implementing subclass to have two constructors, one that wouldn't set someVal , thus relying on the "defaultValue" , another one that sets a different someVal , that is to say, val sc = SubClass() and val sc2 = SubClass("anotherVal")

I have tryied with:

class SubClass() : SuperClass() {
    constructor(someVal: String) : this(someVal)

But the compiler complains:

Error:(5, 37) Kotlin: There's a cycle in the delegation calls chain

How can I implement it keeping someVal immutable? A solution like the following is not valid since it would be mutable:

abstract class SuperClass(var someVal: String = "defaultValue") : SomeSuperClass 


class SubClass() : SuperClass() {
    constructor(someVal: String) : this() {
        super.someVal = someVal
    }
}

Answer 1

If you omit the primary constructor you can do this:

class SubClass : SuperClass {
    constructor(someVal: String): super(someVal)
    constructor(): super()
}