Scala: How to determine the exception type of a Failure

Question

Look at this code snippet:

userService.insert(user) match {
  case Success(f) => Logger.debug("User created successfully")
  case Failure(e) => {
     // how do I determine the type of `e`?
  }
}

How do I determine the type of the exception contained by Failure? I need to take different actions depending on the exception type.

Didier Dupont · Accepted Answer · 2014-01-05 23:28:34Z

19

case Success(f) => 
case Failure(e: ExceptionType1) =>
case Failure(e: ExceptionType2) => 
case Failure(e) => // other

or

case Success(f) =>
case Failure(e) => e match {
   case e1: ExceptionType1 =>
   case e2: ExceptioNType2 =>
   case _ => 
}

answered Jan 5, 2014 at 23:28

Didier Dupont

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4 Comments

Kevin Meredith Over a year ago

@Didier, which seems more idiomatic to you? The latter seems clearer to me since the inner match relates to Exceptions only.

Didier Dupont Over a year ago

Not sure if one of them is more standard. I believe I would use the first one, except if there is a common behavior in case of failure: you may put other instructions than the e match in the Failure case. Both look fine to me, use whichever one suits you.

Hugh Over a year ago

I think the first is much clearer as it avoids nesting; even in the presence of shared behaviour I'd be more inclined to use case Failure(e: Ex1) | Failure(e: Ex2) => ….

Didier Dupont Over a year ago

There might be some behavior common to both exception and some specific to each?

Julia · Accepted Answer · 2023-09-15 01:45:48Z

0

or

case Success(f) =>
case Failure(e @ _: ExceptionType1) =>
case Failure(e @ _: ExceptionType2 | ExceptionType3) =>
case Failure(e) =>

answered Sep 15, 2023 at 1:45

Julia

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