Playframework 2.4.x Json 写 List[(String, String)]

Posted 2023-04-01

【中文标题】Playframework 2.4.x Json 写 List[(String, String)]

【英文标题】：Playframework 2.4.x Json write List[(String, String)]

【发布时间】：2016-02-17 13:45:17

【问题描述】：

我正在尝试更新一些代码。我在尝试编写 json 隐式编写器时遇到此案例类的问题

case class TemplateEmailMessage(recipients: List[EmailRecipient], globalEmailVars: List[(String, String)])

原来是这样

implicit val templateEmailMessageWrites = new Writes[TemplateEmailMessage] 
        def writes(m: TemplateEmailMessage): JsValue = 
            val globalVars: List[JsValue] = m.globalEmailVars.map(g => Json.obj("name" -> g._1, "content" ->g._2))
            Json.obj(
        "to" -> m.recipients,
        "global_merge_vars" -> JsArray(globalVars)
            )
        
    

现在是这样的。显然不起作用，因为第二个字段的类型 List[(String, String)]

object TemplateEmailMessage 

  implicit val templateEmailMessageWrites: Writes[TemplateEmailMessage] = (
    (JsPath \ "to").write[List[EmailRecipient]] and
    (JsPath \ "global_merge_vars").write[List[(String, String)]]
  )(unlift(TemplateEmailMessage.unapply))

我不知道如何翻译 JsArray，因为之前它被用来操作 writer 中的值。我应该像旧方式一样离开还是有其他方式？

谢谢

【参考方案1】：

你可以这样做：

object TemplateEmailMessage
implicit val templateEmailMessageWrites: Writes[TemplateEmailMessage] = (
  (JsPath \ "to").write[List[EmailRecipient]] and
  (JsPath \ "global_merge_vars").write[JsArray]
     .contramap[List[(String, String)]](list => JsArray(list.map(g => Json.obj("name" -> g._1, "content" ->g._2))))
 )(unlift(TemplateEmailMessage.unapply))

其他选项，是将 (String, String) 元组转换为案例类并为其创建编写器。

case class Variable(name: String, content: String)
object Variable
implicit val variableWrites: Writes[Variable] = (
  (JsPath \ "name").write[String] and
  (JsPath \ "content").write[String]
 )(unlift(Variable.unapply))

然后：

implicit val templateEmailMessageWrites: Writes[TemplateEmailMessage] = (
  (JsPath \ "to").write[List[EmailRecipient]] and
  (JsPath \ "global_merge_vars").write[List[Variable]]
)(unlift(TemplateEmailMessage.unapply))