解构会导致未来的错误吗？

Question

Initialy我们有这样的代码

class Person(firstName: String, lastName: String) 

val (firstName, lastName) = person 

有人交换领域

class Person(lastName: String, firstName: String) 

val (firstName, lastName) = person 

编译器是幸福的！

Answer 1

编译器无法知道你交换了字段的顺序，因为分析没有查找参数名称。只要typer类型检查，一切都很好。你可以做的是额外的类型：

case class FirstName(name: String) 
case class LastName(name: String) 

class Person(firstName: FirstName, lastName: LastName) 

现在交换的类型会导致编译时错误。

如果你不想allocationing其他对象的额外开销，看看shapeless tagged types：

import shapeless.tag.@@ 

trait FirstNameTag 
trait LastNameTag 

type FirstName = String @@ FirstNameTag 
type LastName = String @@ LastNameTag 

case class Person(fn: FirstName, ln: LastName) 

现在：

import shapeless.tag 

val firstName: FirstName = tag[FirstNameTag][String]("yuv") 
val lastName: LastName = tag[LastName][String]("itz") 

val person = Person(firstName, lastName) 

或@Ren指出使用value classes：

case class FirstName(name: String) extends AnyVal 
case class LastName(name: String) extends AnyVal