播放案例类的 json 读取和默认参数? [英] Play json Read and Default parameters for case class?

问题描述

我在使用默认参数和使用 Play Json Read 时遇到问题.这是我的代码:

I have a problem with default parameters and using Play Json Read. Here is my code:

  case class Test(action: String, storeResult: Option[Boolean] = Some(true), returndata: Option[Boolean] = Some(true))

  val json =
    """
      {"action": "Test"}"""

  implicit val testReads: Reads[Test] =
    (
      (JsPath \ "action").read[String](minLength[String](1)) and
        (JsPath \ "store_result").readNullable[Boolean] and
        (JsPath \ "returndata").readNullable[Boolean]
      ) (Test.apply _)
  val js = Json.parse(json)

  js.validate[Test] match {
    case JsSuccess(a, _) => println(a)
    case JsError(errors) =>
      println("Here")
      println(errors)
  }

我希望最后得到的是

Test("Test", Some(true), Some(true))

但我得到了:

Test("Test",None,None)

为什么会这样?如果我没有在 json 中提供参数，为什么它没有默认值?如何实现我想要的?

Why is this so? If I didn't provide parameter in the json why it didn't got default value? How to achieve what I want?

推荐答案

看起来好像支持默认参数是在 2.6.

It looks as if support for default parameters is in version 2.6.

以前版本的解决方法是执行以下操作:

A workaround for prior versions is to do something like the following:

object TestBuilder {
  def apply(action: String, storeResult: Option[Boolean], returndata: Option[Boolean]) =
    Test(
      action, 
      Option(storeResult.getOrElse(true)), 
      Option(returndata.getOrElse(true))
    )
}

implicit val testReads: Reads[Test] =
  (
    (JsPath \ "action").read[String](minLength[String](1)) and
    (JsPath \ "store_result").readNullable[Boolean] and
    (JsPath \ "returndata").readNullable[Boolean]
  )(TestBuilder.apply _)

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