val l = List(1,2,3)
val s = l match {
  case list @ List(1, _*) => s"a start value is 1 list :$list"
  case list : List[_] => s"a start value not 1 list"
}

list @ List(1, _*) 不能写成 list : List(1, _*)

@ 把 右侧的值绑定到左侧


val f = Future {2/0}
f.onComplete{
 case result @ _ => println(result)
}


f.onComplete{
 case Success(value) => println(value)
 case Failure(error) => println(error)
}




object PatternMatchDemo {

  def main(args: Array[String]) {

    val rectangle = Rectangle(2, 3)
    val circle = Circle(5)
    val location = Location(7, 9, circle)
    val group = Group(rectangle, circle, location)

    info(rectangle)
    info(circle)
    info(location)
    info(group)

    circle match{
      // 匹配项直接赋值给value
      case value@_ => println(value)
    }

  }

  def info(shape: Shape): Unit = {
    shape match {
      // 匹配项直接赋值给v
      case v@Rectangle(width, height) => println(f"Rectangle ${v}")
      case v@Circle(r) => println(f"Circle ${v},r=${r}")
      case v@Location(x, y, shape) => println(f"Location ${v}")
      // shapes@_*  参数当做数组赋值给变量 shapes
      case Group(shapes@_*) => shapes.foreach(info)
    }
  }


  abstract class Shape

  case class Rectangle(width: Int, height: Int) extends Shape

  case class Circle(radius: Int) extends Shape

  case class Location(x: Int, y: Int, shape: Shape) extends Shape

  case class Group(shape: Shape*) extends Shape
}