Hands-On Design Patterns with Kotlin

Instance checks

Coming from Java, you may be inclined to check what type your object is using, is, and cast it using as:

interface Superheroclass Batman : Superhero {    fun callRobin() {        println("To the Bat-pole, Robin!")    }}class Superman : Superhero {    fun fly() {        println("Up, up and away!")    }}fun doCoolStuff(s : Superhero) {    if (s is Superman) {        (s as Superman).fly()    }    else if (s is Batman) {        (a as Batman).callRobin()    }}

But as you may know, Kotlin has smart casts, so implicit casting, in this case, is not needed:

fun doCoolStuff(s : Superhero) {    if (s is Superman) {        s.fly()    }    else if (s is Batman) {        s.callRobin()    }}

Moreover, in most cases, using when() while smart-casting produces cleaner code:

fun doCoolStuff(s : Superhero) { when(s) { ...