如何模式匹配继承树中的抽象父类

Question

我是scala的新手,拥有java背景.

有没有办法在类继承树中模式匹配超类(或特征),叶子作为案例类和节点抽象类或特征？据我所知,不允许使用case类继承.

我认为在大型继承树中匹配抽象类的模式会非常有用

在下面的代码中,编译期间匹配语句错误的最后一种情况

sealed trait Person {
   def name: String
}

case class Customer(name: String, email: String) extends Person

sealed trait Employee extends Person {
   def id: Int
}

case class Worker(name: String, id: Int, skills: Array[String]) extends Employee

case class Manager(name: String, id: Int, title: String) extends Employee

def process(p: Person) = p match {
   case Customer(_, email) => email
   case Employee(name, _) => name + "@acme.com"
}

Answer 1

您错过了以下对象对象中的name字段Employee和unapply方法Employee:

sealed trait Employee extends Person {
  def id: Int
  def name: String
}

object Employee {
  def unapply(e: Employee): Option[(String, Int)] =
    Option(e) map { e =>
      (e.name, e.id)
    }
}

通过上述更改,处理方法没有出现任何问题:

def process(p: Person) = p match {
  case Customer(_, email) => email
  case Employee(name, _) => name + "@acme.com"
}