Pattern matching with OR logic

Question

For instance, I have two Try objects. I want to get error if one or another fails and process it in the same way:

  val t1 = Try(throw new Exception("one"))
  val t2 = Try(throw new Exception("two"))

  (t1, t2) match {
    case (Success(_), Success(_)) => println("It's ok")
    case _ : Failure(e), _) | (_, Failure(e) =>  // Compile error here

      println("Fail", e)                         // Doesn't matter from where e was come 
  }

Is it possible to make this code with the same e in both failure options compile?

You can't- you can put the futures in a list and flatten it as in https://stackoverflow.com/questions/15495678/flatten-scala-try — Arnon Rotem-Gal-Oz, Jun 28 '18 at 06:37
Is it so bad if you separate the two failing cases? `case (Failure(e), _) => println(s"Fail $e") case (_, Failure(e)) => println(s"Fail $e")` — mfirry, Jun 28 '18 at 06:38
@mfirry Actually, not very bad, but I was wonder if it is possible. — Oleg, Jun 28 '18 at 06:41

score 5 · Accepted Answer · answered Jun 28 '18 at 06:38

5

You cannot combine match patterns this way. You can achieve the desired behaviour this way:

t1.flatMap(_ => t2) match {
   case Success(_) => println("It's ok")
   case Failure(e) => prinltn("Fail", e)
}

answered Jun 28 '18 at 06:38

Nyavro

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Interesting technique. Thank you! – Oleg Jun 28 '18 at 06:44

score 0 · Answer 2 · answered Jun 28 '18 at 12:17

Another convinient way, based on the @Nyavro answer is to combine multiple tryes in a single try via for comprhensions:

 val tryDoIt = for {
   t1 <- Try(throw new Exception("one"))
   t2 <- Try(throw new Exception("two"))
   t3 <- Try(throw new Exception("three"))
 } yield (t1, t2, t3)

 tryDoIt match {
   case Success((x, y, z)) => println(x,y,z)
   case Failure(e) => println(e.getMessage)
 }

Pattern matching with OR logic

2 Answers2