Using the when expression

What if (no pun intended) we want to have more conditions in our if statement?

In Java, we use the switch statement. In Kotlin, there's a when expression, which is a lot more powerful, since it can embed some other Kotlin features.

Let's create a method that's based on the amount of money that  will give cause to suggest a nice birthday gift:

fun suggestGift(amount : Int) : String {
    return when (amount) {
        in (0..10) -> "a book"
        in (10..100) -> "a guitar"
        else -> if (amount < 0) "no gift" else "anything!"
    }
}

As you can see, when also supports a range of values. The default case is covered by the else block. In the following examples, we will elaborate on even more powerful ways to use this expression.

As a general rule, use when if you have more than two conditions. Use if for simple checks.