Try/catch does not compile

Question
1

I would like to know why the following code does not compile

try {
     val n = args(0).toInt
     } catch {
      case e: NumberFormatException => {println("Wrong number")
        val n = 0}
     }

    println(n)
// error: not found: value n

My first idea was that NumberFormatException is not all bad what can happen. Then I replaced it with

case e: Throwable => {println("Anything wrong"); val n = 0}

but the effect is the same.

2

The variable n defined inside the try is not available after the closing curly brace. The same is for the other n-variable defined inside catch.

The problem can be solved by introducing the variable in the same scope as the println -statement that uses it

val n = try { 
    args(0).toInt
  } catch {
    case e: NumberFormatException => {
       println("Wrong number")
       0
    }
}

println(n)
3 Likes
3

Ok, I see. But what if I do not want to return anything in the case of exception, just exit after printing?

4

Well, it depends on where you need the value. You could of course move the normal print inside the try.

try { 
    val n = args(0).toInt
    println(n)
  } catch {
    case e: NumberFormatException => {
       println("Wrong number")
    }
}

Note also that since 2.13 you can also use toIntOption() which gives you an Option[Int] without a need for a try-catch

2 Likes