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Scala Error Handling



Using Try with map, getOrElse and flatMap:

import scala.util.Try
val i = Try("123".toInt) // Success(123) + 1).getOrElse(321) // 124
val j = Try("abc".toInt) // Failure(java.lang.NumberFormatException) + 1).getOrElse(321) // 321
Try("123".toInt) flatMap { i =>
 .map(_ + i)
} // Success(357)

Using Try with pattern matching:

Try(parsePerson("John Doe")) match {
 case Success(person) => println(person.surname)
 case Failure(ex) => // Handle error ...


Different data types for error/success

def getPersonFromWebService(url: String): Either[String, Person] = {
 val response = webServiceClient.get(url)
 response.webService.status match {
 case 200 => {
 val person = parsePerson(response)
 if(!isValid(person)) Left("Validation failed")
 else Right(person)
 case _ => Left(s"Request failed with error code $response.status")

Pattern matching on Either value

getPersonFromWebService("") match {
 case Left(errorMessage) => println(errorMessage)
case Right(person) => println(person.surname)

Convert Either value to Option

val maybePerson: Option[Person] = getPersonFromWebService("").right.toOption


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