Delegated map

So, we learned how to use standard delegates, but Kotlin has to offer more with delegation. The map delegation is among those awesome features that comes with delegation. So, what is it? It is the freedom of passing a map as a single parameter instead of numbers of parameters in a function/class constructor. Let's have a look. The following is a program applying map delegation:

data class Book (val delegate:Map<String,Any?>) { 
    val name:String by delegate 
    val authors:String by delegate 
    val pageCount:Int by delegate 
    val publicationDate:Date by delegate 
    val publisher:String by delegate 
} 
 
fun main(args: Array<String>) { 
    val map1 = mapOf( 
            Pair("name","Reactive Programming in Kotlin"), 
            Pair("authors","Rivu Chakraborty"), 
            Pair("pageCount",400), 
            Pair("publicationDate",SimpleDateFormat("yyyy/mm/dd").parse("2017/12/05")), 
            Pair("publisher","Packt") 
    ) 
    val map2 = mapOf...