Kotlin Crash Course for Programmers/

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Conditions as Expressions

Conditions as Expressions

Learn how to use conditions in Kotlin as expressions, including assigning different values to a variable depending on a condition.

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In Kotlin, both if and when can be used as expressions instead of statements. An expression is a piece of code that has a value, e.g. "Kotlin", 42 * 17, or readInput(). In contrast, a statement is a piece of code with no value, such as fun foo() { ... } or while (active) { ... }. In many programming languages, if and when/switch are statements. But in Kotlin, they are expressions! Let’s explore how this works.

Expressions with if #

Recall this listing from the lesson on if statements:

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if (planet == "Jupiter") {
  println("Radius of Jupiter is 69,911km")
} else if (planet == "Saturn") {
  println("Radius of Saturn is 58,232km")
} else {
  println("No data for planet $planet")
}

If you think about it, it seems that the relevant data that changes here based on the condition is the radius. So let’s store that in a variable by using an if ...