The use of generics and vararg variable parameters in kotlin

//Kotlin Medium generics and vararg The use of variable parameters 
class KtBase10<T>(vararg objects: T, var isMap: Boolean) {
    //out  there T Can only be read , Do not modify 
    private val objectArray: Array<out T> = objects

    fun showObj(index: Int): T? = objectArray[index].takeIf { isMap } ?: null

    fun <O> mapObj(index: Int, mapAction: (T?) -> O): O? = mapAction(objectArray[index].takeIf { isMap })
//    fun <O> mapObj(index: Int, mapAction: (T?) -> O): O? {
//        return mapAction(objectArray[index].takeIf { isMap })
//    }
}

fun main(args: Array<String>) {
    val p: KtBase10<Any?> = KtBase10("yuknight", 123, 22.1f, null, 'A', isMap = true)
    println(p.showObj(0))
    println(p.showObj(1))
    println(p.showObj(2))
    println(p.showObj(3))
    println(p.showObj(4))
    println()
    var r: Any? = p.mapObj(0) {
        it.toString().length
    }
    println(r)//8
    var r1 = p.mapObj(1) { obj: Any? ->
//        obj.toString().length
        " The second parameter is ：$obj"
    }
    println(r1)// The second parameter is ：123
    //
    val p2: KtBase10<String> = KtBase10("AAA", "BBB", "CCCC", isMap = true)
    val r3 = p2.mapObj(0){
        it
        " Turn into String type ：$it"
    }
    println(r3)// Turn into String type ：AAA
    val r4 = p2.mapObj(2){
        str: String? ->  " Turn into String type ：$str"
    }
    println(r4)// Turn into String type ：CCCC

}