How to add multiple statements inside a when statement in kotlin

Question

I am trying to have multiple statements for one condition. For example: this is a sample code for when statement.

when (x) {
    1 -> print("x == 1")
    2 -> print("x == 2")
     else -> { // Note the block
        print("x is neither 1 nor 2")
   }
}

When x is 1, I also want to have an extra statement like x += 10, how can I do it?

Solution

You have the solution in your question with the "Note the block" comment. Branches of when can be blocks that can contain any number of statements:

when(x) {
    1 -> {
        println("x == 1")
        x += 10
        println("x == 11")
    }
    2 -> { ... }
    else -> { ... }
}

Writing a single statement branch just has a simplified syntax so that you don't need to surround it with {}.

Comments

[marstran]

That's a bit weird. Everywhere else in the language, adding braces means it's a lambda. How would you make a when-expression that returns a lambda of type () -> Unit?

[zsmb13]

Hmm, that's a rather interesting question. You can do -> { { println("hello") } }, for example. The lambda is the last statement in the branch, and will be returned. You could also do -> fun() { println("hello") }, that might be more legible.

[voddan]

The nicest way IMO is -> ({}). And I totally agree it is weird

[zsmb13]

Ah, that is pretty neat, actually.