Kotlin companion, 2024-03-18

class Book private constuctor(val id: Int, val name : String){
   companion object BookFactory : IdProvider{
      override fun getId() : Int {
          return 202
      }
      val myBook = "new book"
      fun create()= Book(getId(), myBook)
   }
}

interface IdProvider {
   fun getId() : Int
}

fun main(){
   val book = Book.create()
   val bookId = Book.BookFactory.getId()
   println("${book.id} ${book.name}")
}