class student{

  def sayHello(name: => String){

    println(s"Hello, $name, welcome $name")

  }

}

object FunctionDemo3 {

  def main(args: Array[String]): Unit = {

    val s = new student()

    def getSName(s: String): String = {println("call"); s}

    //传名参数

    s.sayHello("Sky")

    s.sayHello(getSName("Sky"))

  }

}

Hello, Sky, welcome Sky

call

call

Hello, Sky, welcome Sky