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)
}
What I was hoping to get at the end is
Test("Test", Some(true), Some(true))
but I got:
Test("Test",None,None)
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?
在Play 2.6中你可以写简单:
Json.using[Json.WithDefaultValues].reads[Test]
It looks as if support for default parameters is in version 2.6 .
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 _)
Do you really need Options in your case class if you supply default values? Without Options the following code should work
case class Test(action: String, storeResult: Boolean = true, returndata: Boolean = true)
implicit val testReads: Reads[Test] =
(
(JsPath \\ "action").read[String](minLength[String](1)) and
((JsPath \\ "store_result").read[Boolean] or Reads.pure(true)) and
((JsPath \\ "returndata").read[Boolean] or Reads.pure(true))
) (Test.apply _)
If you need Options then this code might work (not tested!)
case class Test(action: String, storeResult: Option[Boolean] = Some(true), returndata: Option[Boolean] = Some(true))
implicit val testReads: Reads[Test] =
(
(JsPath \\ "action").read[String](minLength[String](1)) and
((JsPath \\ "store_result").read[Boolean] or Reads.pure(true)).map(x=>Some(x)) and
((JsPath \\ "returndata").read[Boolean] or Reads.pure(true)).map(x=>Some(x))
) (Test.apply _)
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