Scala变量有多种类型(Scala variable with multiple types)

Scala变量有多种类型(Scala variable with multiple types)

在scala中有一个允许一个变量有2个类型值的方法。

val x: Either[String, Int] = Left("apple")

但是，我想为变量x有两种以上的类型，例如{String, Int, Double, List[String] } 。

e.g. val x:[type can be either String, Int, Double or List[String]] //So that I can store either String, Int, Double, List[String] value in x.

有什么办法可以做到这一点？

There is Either in scala which allow a variable to have 2 types value.

val x: Either[String, Int] = Left("apple")

However, I want to have more than 2 types for variable x e.g. {String, Int, Double, List[String] }.

e.g. val x:[type can be either String, Int, Double or List[String]] //So that I can store either String, Int, Double, List[String] value in x.

Is there any way to achieve this?

最满意答案

IMO最自然的表达方式是创建一个ADT（代数数据类型）：

sealed trait Foo case class Bar(s: String) extends Foo case class Baz(i: Int) extends Foo case class Fizz(d: Double) extends Foo case class Buzz(l: List[String]) extends Foo

现在你可以在Foo上进行模式匹配：

val f: Foo = ??? f match { case Bar(s) => // String case Baz(i) => // Int case Fizz(d) => // Double case Buzz(l) => // List[String] }

IMO the most natural way to express this is to create an ADT (Algebraic Data Type):

sealed trait Foo final case class Bar(s: String) extends Foo final case class Baz(i: Int) extends Foo final case class Fizz(d: Double) extends Foo final case class Buzz(l: List[String]) extends Foo

And now you can pattern match on Foo:

val f: Foo = ??? f match { case Bar(s) => // String case Baz(i) => // Int case Fizz(d) => // Double case Buzz(l) => // List[String] }