Class delegation

Class delegation is another interesting feature of Kotlin. How? Just think of the following situation.

You have an interface, I, and two classes, A and B. Both A and B implement I. In your code, you've an instance of A and you want to create an instance of B from that A.

In traditional inheritance, it is not directly possible; you have to write a bunch of nasty codes to achieve that, but class delegation is there to save you.

Go through the following code:

interface Person { 
    fun printName() 
} 
 
class PersonImpl(val name:String):Person { 
    override fun printName() { 
        println(name) 
    } 
} 
 
class User(val person:Person):Person by person { 
    override fun printName() { 
        println("Printing Name:") 
        person.printName() 
    } 
} 
 
fun main(args: Array<String>) { 
    val person = PersonImpl("Mario Arias") 
    person.printName() 
    println() 
    val user = User(person) 
    user.printName() 
} 

In this program, we created the instance...