Scala: Declare val in if condition

You can keep the scope really tight:

val result = {
  val tmp = methodCall()
  if (tmp>0) tmp else tmp+23
}

Or use match

methodCall() match {
   case x if x <= 0 => x + 23
   case x => x
}

Starting Scala 2.13, the chaining operation pipe can be used to convert/pipe a value with a function of interest, and thus avoids an intermediate variable:

import scala.util.chaining._

13.pipe(res => if (res > 0) res else res + 23 ) // 13

This is actually a very close variant of a match statement and can as well be written as such:

-27 pipe { case res if (res > 0) => res case res => res + 23 } // -4

You could fold over a single element collection.

Seq(conditionMethod(..)).fold(0){case (z,x) =>
  if (x>z) x+23  // any action as long as the result is an Int
  else     x
}

If your "action" doesn't result in an Int then you could use foldLeft. Here's the same thing returning a String.

Seq(conditionMethod(..)).foldLeft(""){case (_,x) =>
  if (x>0) {
    x+23  // any action as long as if/else types match
    "string"
  }
  else "xxx"
}