Hi everyone! Kind of a weird question but I’m trying to restrict access to a method for any subclas...

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[Antoine Gagnon]

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?

[mazorius]

Can you define the variable like this:

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

[Antoine Gagnon]

I can’t because I won’t be able to access it with AnimalBuilder().dog for instance

[Joris PZ]

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?

[Marc Knaup]

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.")

[Marc Knaup]

It’s also weird that your DogBuilder is inner in AnimalBuilder and also a subclass of AnimalBuilder. So it’s linked to two different AnimalBuilder instances 🤔

[Antoine Gagnon]

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)
    }
}

[Marc Knaup]

Difficult to say without seeing the broader picture 😉

[Antoine Gagnon]

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

[Marc Knaup]

How do you get the final result out of it?

[Antoine Gagnon]

Something like a build function that would be part of AnimalBuilderBase and would return the concatenation of all of those

[Marc Knaup]

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

[Marc Knaup]

I’ve used toString() but you can also use build().

[Antoine Gagnon]

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