"parcel hentai" - parcel with polymorphic field thrue parcelize

MainActivity.kt

package com.example.parcel_hentai


import android.app.Activity
import android.os.Bundle
import android.os.Parcel
import android.os.Parcelable
import android.util.Log
import kotlinx.android.parcel.Parceler
import kotlinx.android.parcel.Parcelize
import kotlinx.android.parcel.TypeParceler


class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        
        val p = Parcel.obtain().apply {
            writeList(listOf(Foo(Bar1(111)), Foo(Bar2("hello")), Foo(Bar())))
        }

        val loader = Foo::class.java.classLoader
        val result = mutableListOf<Any?>()

        p.apply {
            setDataPosition(0)
            readList(result, loader)
            recycle()
        }

        Log.d("FooResults", "[${result.joinToString(", ")}]")
    }
}

@Parcelize
@TypeParceler<Bar, BarParceler>()
data class Foo(val bar: Bar) : Parcelable

@Parcelize
open class Bar : Parcelable {
    override fun toString(): String = "undefinedBar"
}

@Parcelize
data class Bar1(val i: Int) : Bar()

@Parcelize
data class Bar2(val s: String) : Bar()

object BarParceler : Parceler<Bar> {
    private const val TYPE_BAR_UNDEFINED = 0
    private const val TYPE_BAR1 = 1
    private const val TYPE_BAR2 = 2

    override fun create(parcel: Parcel): Bar {
        val b = when (parcel.readInt()) {
            TYPE_BAR1 -> Bar1(parcel.readInt())
            TYPE_BAR2 -> Bar2(parcel.readString()!!)
            else -> Bar()
        }

        Log.d("BarParceler", "read $b")
        return b
    }

    override fun Bar.write(parcel: Parcel, flags: Int) {
        Log.d("BarParceler", "write $this")
        when (this) {
            is Bar1 -> {
                parcel.writeInt(TYPE_BAR1)
                parcel.writeInt(i)
            }
            is Bar2 -> {
                parcel.writeInt(TYPE_BAR2)
                parcel.writeString(s)
            }
            else -> {
                parcel.writeInt(TYPE_BAR_UNDEFINED)
            }
        }
    }
}

output.log

2022-03-02 15:41:06.780 12219-12219/? D/BarParceler: write Bar1(i=111)
2022-03-02 15:41:06.780 12219-12219/? D/BarParceler: write Bar2(s='hello')
2022-03-02 15:41:06.780 12219-12219/? D/BarParceler: write undefinedBar
2022-03-02 15:41:06.780 12219-12219/? D/BarParceler: read Bar1(i=111)
2022-03-02 15:41:06.780 12219-12219/? D/BarParceler: read Bar2(s='hello')
2022-03-02 15:41:06.780 12219-12219/? D/BarParceler: read undefinedBar
2022-03-02 15:41:06.796 12219-12219/? D/FooResults: [Foo(bar=Bar1(i=111)), Foo(bar=Bar2(s='hello')), Foo(bar=undefinedBar)]