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scalafold

Scala fold on Option return type

I am very new to Scala and i would like to return a Some[String] or a None after doing some loging but it seems the types returned are not consistent for the fold to work.

(Option[String]).fold{
            logger.info("Message append failed")
            None
          }{stuff=>
            logger.info("Message appended")
            Some(stuff)
          }

The returned compiler error is the following Expression of type Some[String] does not conform to expected type None.type

Solution

  • I think, you use the wrong type signature. You have to call the fold method on some Option instance. For example:

    scala> val opt = Option("test")
scala> opt.fold[Option[String]] {
     | println("Message append failed.")
     | None
     | } { stuff =>
     | println("Message appended!")
     | Some(stuff)
     | }
Message appended!
res3: Option[String] = Some(test)