Hi everyone! Kind of a weird question but I’m trying to restrict access to a method for any subclass. I’m trying to make a builder like this:

open class AnimalBuilder {
    val dog: DogBuilder get() = DogBuilder()

    open inner class DogBuilder : AnimalBuilder() {
        val pug: PugBuilder get() = PugBuilder()

        inner class PugBuilder : DogBuilder()
    }
}

val pugBuilder = AnimalBuilder().dog.pug 
val wrongBuilder = AnimalBuilder().dog.dog.dog

But as you can see, I don’t want the

DogBuilder

to be able to access the

dog

variable available in

AnimalBuilder

. Is there any way to do that?

Can you define the variable like this:

private val dog: DogBuilder get() = DogBuilder()

I can’t because I won’t be able to access it with

AnimalBuilder().dog

for instance

I don't think there's a visibility modifier than can hide a property from 'grandchildren' subclasses. Is it really necessary that these builders are related through inheritance?

The builders are a little weird. Ideally you’d use

interface

for each and the classes and class hierarchies are merely an implementation detail. Then you are way more flexible in composing different interfaces and the functionality each has. If you really want to keep it like it is then you can hide

dog

in the subclass by overriding it. 1. Mark the

dog

in

AnimalBuilder

as

open

. 2. Add inaccessible

dog

to `DogBuilder`:

@Deprecated(message = "You already have a dog.", level = DeprecationLevel.HIDDEN)
    override val dog: Nothing
        get() = error("Cannot be used.")

I’ve cleaned it up a bit, and it seems like composition might work better with something like this:

open class AnimalBuilderBase(parent: AnimalBuilderBase? = null)

open class AnimalBuilder : AnimalBuilderBase() {
    val dog: DogBuilder get() = DogBuilder(this)

    open class DogBuilder(parent: AnimalBuilder) : AnimalBuilderBase(parent) {
        val pug: PugBuilder get() = PugBuilder(this)

        class PugBuilder(parent: DogBuilder) : AnimalBuilderBase(parent)
    }
}

Difficult to say without seeing the broader picture 😉

The end goal is to be able to get a string that is a composition of all the different levels, so for something like

AnimalBuilder().dog.pug

I would get

Dog - Pug

but for

AnimalBuilder().dog.greyhound

I would get

Dog - Greyhound

with the DogBuilder level adding only the “Dog” string and the PugBuilder level adding the “Pug” string

How do you get the final result out of it?

Something like a

build

function that would be part of

AnimalBuilderBase

and would return the concatenation of all of those

Here’s another approach: https://pl.kotl.in/vwqBnaNLi

I like that a lot too! Thanks for the help. much appreciated!