Scala多种类型模式匹配

我想知道如何使用多种类型模式匹配。我有：

abstract class MyAbstract

case class MyFirst extends MyAbstract
case class MySecond extends MyAbstract
case class MyThird extends MyAbstract // shouldn't be matched and shouldn't call doSomething()

val x: MyAbstract = MyFirst

x match { 
 case a: MyFirst => doSomething()
 case b: MySecond => doSomething()
 case _ => doSomethingElse()
}

所以我想写一些类似的东西：

x match {
 case a @ (MyFirst | MySecond) => doSomething()
 case _ => doSomethingElse()
}

我在一些教程中看到了类似的构造，但是它给了我错误：

pattern type is incompatible with expected type;
[error]  found   : object MyFirst
[error]  required: MyAbstract

那么有没有办法在on case子句中定义几种不同的类型？我认为这会使代码更漂亮。好像我将拥有5个一样，我将编写5次相同的代码（调用doSomething（））。

提前致谢！

您缺少案例类的括号。不推荐使用不带参数列表的案例类。

试试这个：

abstract class MyAbstract
case class MyFirst() extends MyAbstract
case class MySecond() extends MyAbstract

val x: MyAbstract = MyFirst()


x match {
   case aOrB @ (MyFirst() | MySecond()) => doSomething(aOrB)
   case _ => doSomethingElse()
}

如果案例类的参数太多，并且不喜欢编写长Foo(_,_,..)模式，那么也许：

x match {
   case aOrB @ (_:MyFirst | _:MySecond) => doSomething(aOrB)
   case _ => doSomethingElse()
}

要不就：

x match {
   case _:MyFirst | _:MySecond => doSomething(x) // just use x instead of aOrB
   case _ => doSomethingElse(x)
}

但是也许您只是想要单例对象？

abstract class MyAbstract
case object MyFirst extends MyAbstract
case object MySecond extends MyAbstract

val x: MyAbstract = MyFirst

x match {
   case aOrB @ (MyFirst | MySecond) => doSomething()
   case _ => doSomethingElse()
}