json - 播放 json 变形金刚地图可选字段

Question

我有以下播放框架 2.3 json 转换器

val transAddress = (
  (__ \ 'address \ 'line1).json.copyFrom( (__ \ 'line1).json.pick ) and
  (__ \ 'address \ 'line2).json.copyFrom( (__ \ 'line2).json.pick ) and
  (__ \ 'address \ 'line3).json.copyFrom( (__ \ 'line3).json.pick ) and

  (__ \ 'address \ 'line4).json.copyFrom( (__ \ 'line4).json.pick ) and

  (__ \ 'address \ 'postcode).json.copyFrom( (__ \ 'postcode).json.pick ) reduce
)

所以这：

{
    line1: "My Street",
    line2: "My Borough",
    line3: "My Town",
    line4: "My County"
}

应该转变为：

{
    address: {
        line1: "My Street",
        line2: "My Borough",
        line3: "My Town",
        line4: "My County"
    }
}

我的问题是在源 json 模型中，line4 是可选的，所以我只想将它映射到 address.line4 可选。所以：

{
    line1: "My Street",
    line2: "My Borough",
    line3: "My Town"
}

也应该转变为：

{
    address: {
        line1: "My Street",
        line2: "My Borough",
        line3: "My Town"
    }
}

我不知道如何使用这些变压器来做到这一点，并且经过大量谷歌搜索后找不到类似的问题。

谢谢！网卡

Answer 1

Option与_readNullable

import play.api.libs.functional.syntax._
import play.api.libs.json._
case class Address(line1: String, line2: String, line3: String, line4: Option[String])

object Address {
  implicit val reads: Reads[Address] = (
      (JsPath \ "line1").read[String] and
      (JsPath \ "line2").read[String] and
      (JsPath \ "line3").read[String] and
      (JsPath \ "line4").readNullable[String]
    )(Address.apply _)
}