case class和case object模式匹配实验

joe

/**
  * @Author Joe_Liang
  * @Date 2021/10/18 15:59
  * @Version 1.0
  */
case class SubmitTask(id:String,name:String)
case class HeartBeat(time:Long)
case object CheckTimeOutTask
object caseTest {
  def main(args: Array[String]): Unit = {
    val arr = Array(CheckTimeOutTask,SubmitTask("123","zs"),HeartBeat(12333333))
    for(i <- 0 until 10) {
      arr(Random.nextInt(arr.length)) match {
        case SubmitTask(id,name) => println(s"${id} ${name}")
        case HeartBeat(time) => println(time)
        case CheckTimeOutTask => println("checktimeouttask")
      }
    }
  }
}
显示如下：
123 zs
12333333
12333333
checktimeouttask
12333333
12333333
checktimeouttask
123 zs
checktimeouttask
123 zs

joe

其实arr的类型是Array[Product with Serializable]。如果用下面的代码：
    val st = SubmitTask("123","lisi")
    val hb = HeartBeat(12345)
    st match {
      case HeartBeat(time) => println(time)
      case HeartBeat(time) => println(time)
      case SubmitTask(id,name) => println(id + name)
    }
则出现编译错误：
Error24, 12) constructor cannot be instantiated to expected type;
found   : HeartBeat
required: SubmitTask
这里出现错误是因为类型不同，匹配异常。