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Continuing our break from the Koans today and going to look at another cool trick I learnt using Kotlin this week and focusing on the when keyword we learnt about previously;
Let’s start with a simple function to return the text for a value using when:
fun step1(number: Int):String {
var result = "";
when (number) {
0 -> result = "Zero"
1 -> result = "One"
2 -> result = "Two"
}
return result;
}
The next evolution is we can avoid creating a variable and returning directly (this is something I would do often in .NET)
fun step2(number: Int):String {
when (number) {
0 -> return "Zero"
1 -> return "One"
2 -> return "Two"
}
return ""
}
And now we get to the cool part, we can just return the when!
fun step3(number: Int):String {
return when (number) {
0 -> “Zero”
1 -> “One”
2 -> “Two”
else -> “”
}
}
Yup, the when can return a value which means we can also do one final trick:
fun step4(number: Int):String = when (number) {
0 -> "Zero"
1 -> "One"
2 -> "Two"
else -> ""
}
It is so cool that your logic can just return from a condition, and it works with if statements too and even with the Elvis operator we learnt yesterday:
fun ifDemo3(name:String?) = name ?: "Mysterious Stranger"