如何在状态中复制 class？

Question

如果State中所有的val都是基本数据类型就很简单了。如果我们想在其中复制一个特定的值，它只是

copy(specificValue = newValue)

但是如果这个特定值在 class 内怎么办？这是我试过但无济于事

copy(specificClass.specificValue = newValue)

我应该 create/copy 这个 class 在外面，然后像下面这样吗？

copy(specificClass = newClass)

Answer 1

如果你有


case class Address(street: String, city: String)
case class User(address: Address, name: String)

val u = User(...)

//to change the city to something else you would do

val another = u.copy(address = u.address.copy(city = "New York")

这很麻烦。我建议使用 quicklens 库，它可以让你写：


 import com.softwaremill.quicklens._

 val another = u.modify(_.address.city).setTo("New York")

Answer 2

这是一个名为quicklens

的项目

import com.softwaremill.quicklens._

case class Street(name: String)
case class Address(street: Street)
case class Person(address: Address, age: Int)

val person = Person(Address(Street("1 Functional Rd.")), 35)

val p2 = person.modify(_.address.street.name).using(_.toUpperCase)
val p3 = person.modify(_.address.street.name).setTo("3 OO Ln.")

// or

val p4 = modify(person)(_.address.street.name).using(_.toUpperCase)
val p5 = modify(person)(_.address.street.name).setTo("3 OO Ln.")

如何在状态中复制 class？

how to copy a class inside of a state?

scala

copy

lagom