25 scala 模式匹配.adoc

25 scala 模式匹配

list 模式匹配

object For_Advanced {

  def main(args: Array[String]): Unit = {
    for (i <- List(1, 2, 3, 4, 5)) {
      println(i)
    }

    for (index@"Flink" <- List("Hadoop", "Spark", "Flink")) {
      println(index)
    }

    for ((language, "Hadoop") <- Set("Scala" -> "Spark", "Java" -> "Hadoop")) println(language)
    for ((k, v: Int) <- List(("Spark" -> 5), ("Hadoop" -> "Big Data"))) {
      println(k)
    }
  }

}

元组模式匹配

object Assinment_Internals {

  def main(args: Array[String]) {
    val a@b = 1000
    println("a = " + a + ", b = " + b)
    val (c, d) = (1000, 2000)
    //    val (e,F) = (1000,2000)
    val Array(g, h) = Array(1000, 2000)
    //    val Array(i,J) = Array(1000,2000)
    //    object Test { val 1 = 1 }
    object Test {
      val 1 = 2
    }

  }

}

提取器

object :> {
  def unapply[A](list: List[A]) = {
    Some((list.init, list.last))
  }
}

object Extractor_Advanced {

  def main(args: Array[String]) {
    (1 to 9).toList match {
      case _ :> 9 => println("Hadoop")
    }
    (1 to 9).toList match {
      case x :> 8 :> 9 => println("Spark")
    }
    (1 to 9).toList match {
      case :>(:>(_, 8), 9) => println("Flink")
    }

  }

}