Try وSuccess وFailure

ما هي Try؟

استيراد Try

import scala.util.Try

@main def run(): Unit = {
  val ok = Try(10 / 2)
  val bad = Try(10 / 0)
  println(ok)
  println(bad)
}

‏Success وFailure

import scala.util.{Try, Success, Failure}

@main def run(): Unit = {
  val result = Try("123".toInt)
  result match {
    case Success(n) => println(s"parsed: $n")
    case Failure(e) => println(s"failed: ${e.getMessage}")
  }
}

مطابقة أنماط حالات الفشل

import scala.util.{Try, Success, Failure}

@main def run(): Unit = {
  val result = Try("abc".toInt)
  result match {
    case Success(n) => println(s"got $n")
    case Failure(e) => println(s"error type: ${e.getClass.getSimpleName}")
  }
}

‏getOrElse مع Try

import scala.util.Try

@main def run(): Unit = {
  val n = Try("oops".toInt).getOrElse(-1)
  println(n)
}

‏map مع Try

import scala.util.Try

@main def run(): Unit = {
  val doubled = Try("21".toInt).map(_ * 2)
  val failed  = Try("x".toInt).map(_ * 2)
  println(doubled)
  println(failed)
}

‏recover: معالجة الاستثناء

import scala.util.Try

@main def run(): Unit = {
  val safe = Try("x".toInt).recover {
    case _: NumberFormatException => 0
  }
  println(safe)
}

‏recoverWith

import scala.util.Try

@main def run(): Unit = {
  val result = Try("x".toInt).recoverWith {
    case _: NumberFormatException => Try("42".toInt)
  }
  println(result)
}

‏toEither وtoOption

import scala.util.Try

@main def run(): Unit = {
  println(Try("5".toInt).toOption)
  println(Try("x".toInt).toOption)
  println(Try("5".toInt).toEither.isRight)
}

التسلسل باستخدام flatMap

import scala.util.Try

object Main {
  def half(n: Int): Try[Int] = Try(if (n % 2 == 0) n / 2 else throw new RuntimeException("odd"))

  def main(args: Array[String]): Unit = {
    println(Try("8".toInt).flatMap(half))
    println(Try("7".toInt).flatMap(half))
  }
}

‏Try مقابل try/catch

تحقق سريع

مراجعة