Hi! Is there an easy way to raise an error from a ...

# arrow

[jean]

Hi! Is there an easy way to raise an error from a map operator? I have this code :

Either.catch {
    val tickets = repository.inspect(qrContent = capturedCode.rawValue) // can throw
    if (tickets == null) {
        travelDocumentHelper.showTicketInspectionFailure(null)
        ReadTravelDocumentError.NoTicketFound // <- How can I "raise" this error as a `Either.Left`?
    } else {
        successfulTicketInspectionHandler.handleSuccessfulTicketInspection(tickets) // <- regular `Either.Right`
    }
}.mapLeft {
    travelDocumentHelper.showTicketInspectionFailure(it)
    Log.error(TAG, "Cannot read QR data: ${capturedCode.rawValue}, exception: $it")
    ReadTravelDocumentError.FailedToInspect
}

But the problem here is that my “right” type is Any instead of Unit . It works with a throw inside the catch but it would have been nicer with a raise(...)

[Alejandro Serrano.Mena]

Either.catch only "handles" the exceptions. If you want to also raise within a block, the best is using either block, and use catch inside

either {
  try {
    val tickets = repository.inspect(qrContent = capturedCode.rawValue)
    ensureNotNull(tickets) { ReadTravelDocumentError.NoTicketFound }
    successfulTicketInspectionHandler.handleSuccessfulTicketInspection(tickets)
  } catch {
    raise(ReadTravelDocumentError.FailedToInspect)
  }
}.onLeft {  
  travelDocumentHelper.showTicketInspectionFailure(it)
  Log.error(TAG, "Cannot read QR data: ${capturedCode.rawValue}, exception: $it")
}

[jean]

Thanks!