class UserResponse(val map: Map<String, Any?>) {
    val user: User by map
}

class User(val map: Map<String, Any?>) {
    val name: String by map
    val age: Int     by map
}

fun main(args: Array<String>) {
    val user = mapOf(
            "name" to "Jack",
            "age" to 40
    )
    val response = mapOf(
            "user" to User(user)
    )

    val userResponse = UserResponse(response)
    println(userResponse.user.name) // Prints "Jack"
    println(userResponse.user.age)  // Prints 40
}