Scala案例有22個字段，但在scala 2.11.5中有play-json問題

Question

使用Scala 2.11，我們可以在一個案例類中擁有超過22個字段嗎？

case class SomeResponse(
                                     var compositeKey: String,
                                     var id1: String,
                                     var id2: String,
                                     var firstName: String,
                                     var lastName: String,
                                     var email: String,
                                     var email2: String,
                                     var birth: Long,
                                     var gender: String,
                                     var phone: Phone,
                                     var city: String,
                                     var zip: String,
                                     var carriage: Boolean,
                                     var carriage2: Boolean,
                                     var fooLong: Long,
                                     var fooLong2: Long,
                                     var suspended: Boolean,
                                     var foo: Foo,
                                     var address: String,
                                     var suite: String,
                                     var state: String,
                                     var instructions: String)

implicit val formatSomeResponse = Json.format[SomeResponse]

以上是一個案例類，其中有正好22個字段與play-json格式，現在當我編譯時，我得到這個錯誤：

SomeFile.scala:126: value apply is not a member of play.api.libs.functional.FunctionalBuilder[play.api.libs.json.OFormat]#CanBuild22[String,String,String,String,String,String,String,Long,String,com.Phone,String,String,Boolean,Boolean,Long,Long,Boolean,com.Foo,String,String,String,String]

案例類Phone和Foo各有兩個字段。

所以，為什么我實際上面對這個問題，它沒有超過22個字段的限制，或者是否有其他我做錯了，我在scala 2.11.5 / 2.11.1中嘗試過- play-json 2.3

更新：根據James和Phadej的回答

  val someResponseFirstFormat: OFormat[(String, String, String, String, String, String, String, Long, String, Phone, String)] =
    ((__ \ "compositeKey").format[String] and
      (__ \ "id1").format[String] and
      (__ \ "id2").format[String] and
      (__ \ "firstName").format[String] and
      (__ \ "lastName").format[String] and
      (__ \ "email").format[String] and
      (__ \ "email2").format[String] and
      (__ \ "birth").format[Long] and
      (__ \ "gender").format[String] and
      (__ \ "phone").format[Phone] and
      (__ \ "city").format[String]).tupled

  val someResponseSecondFormat: OFormat[(String, Boolean, Boolean, Long, Long, Boolean, Foo, String, String, String, String)] =
    ((__ \ "zip").format[String] and
      (__ \ "carriage").format[Boolean] and
      (__ \ "carriage2").format[Boolean] and
      (__ \ "fooLong").format[Long] and
      (__ \ "fooLong2").format[Long] and
      (__ \ "suspended").format[Boolean] and
      (__ \ "foo").format[Foo] and
      (__ \ "address").format[String] and
      (__ \ "suite").format[String] and
      (__ \ "country").format[String] and
      (__ \ "instructions").format[String]).tupled

  implicit val formatSome: Format[SomeResponse] = (
    someResponseFirstFormat and someResponseSecondFormat
    ).apply({
    case ((compositeKey, id1, id2, firstName, lastName, email, email2, birth, gender, phone, city),
    (zip, carriage, carriage2, created, updated, suspended, foo, address, suite, country, instructions)) =>
      SomeResponse(compositeKey, id1, id2, firstName, lastName, email, email2, birth, gender, phone, city, zip, carriage, carriage2, created, updated, suspended, location, address, suite, country, instructions)
  }, huge => ((huge.compositeKey, huge.id1, huge.id2, huge.firstName, huge.lastName, huge.email, huge.email2, huge.birth, huge.gender, huge.phone, huge.city),
    (huge.zip, huge.carriage, huge.carriage2, huge.created, huge.updated, huge.suspended, huge.foo, huge.address, huge.suite, huge.country, huge.instructions)))

Answer 1

您可以拆分您的Reads定義：

val fields1to10: Reads[(A,B,C,D,E,F,G,H,I,J)] = ???
val fields11to20 = ???
val fields21to30 = ???

implicit val hugeCaseClassReads: Reads[HugeCaseClass] = (
  fields1to10 and fields11to20 and fields21to30
) { a, b, c => createHugeCaseClassFromThreeTuples(a, b, c) }

---

“功能語法”不適用於超過22個字段的原因是因為存在最多只定義22個的中間類： FunctionalBuilder

---

完全寫出小例子它看起來像：

import play.api.libs.json._
import play.api.libs.functional.syntax._

// Let's pretend this is huge:
case class Huge(a: Int, b: String, c: Boolean, d: List[Int])

val fields1to2: Reads[(Int, String)] = (
  (__ \ "a").read[Int] and
  (__ \ "b").read[String]
).tupled

val fields3to4: Reads[(Boolean, List[Int])] = (
  (__ \ "c").read[Boolean] and
  (__ \ "d").read[List[Int]]
).tupled

implicit val hugeCaseClassReads: Reads[Huge] = (
  fields1to2 and fields3to4
) {
  case ((a, b), (c, d)) =>  
    Huge(a, b, c, d)
}

並且tryint驗證null的結果：

scala> JsNull.validate[Huge]
res6: play.api.libs.json.JsResult[Huge] = JsError(
  List(
    (/b,List(ValidationError(error.path.missing,WrappedArray()))),
    (/d,List(ValidationError(error.path.missing,WrappedArray()))),
    (/c,List(ValidationError(error.path.missing,WrappedArray()))),
    (/a,List(ValidationError(error.path.missing,WrappedArray())))))

如您所見，所有字段都已嘗試過。

---

或者您可以使用更多CanBuildNN類擴展游戲： https ： //github.com/playframework/playframework/blob/2.3.6/framework/src/play-functional/src/main/scala/play/api/libs/functional /Products.scala

---

然而，我建議你在SomeResponse類中對字段進行SomeResponse ，例如地址相關等。如果JSON結構是扁平的並且無法更改，則手動編寫Reads和Writes實例。

Answer 2

為了使上面的例子編譯，我必須使類型顯式：

import play.api.libs.json._
import play.api.libs.functional.syntax._

// Let's pretend this is huge:
case class Huge(a: Int, b: String, c: Boolean, d: List[Int])

object Huge {
  val fields1to2: Reads[(Int, String)] = (
    (__ \ "a").read[Int] and
    (__ \ "b").read[String]
  ).tupled

  val fields3to4: Reads[(Boolean, List[Int])] = (
    (__ \ "c").read[Boolean] and
    (__ \ "d").read[List[Int]]
  ).tupled

  val f: ((Int, String), (Boolean, List[Int])) => Huge = {
    case ((a, b), (c, d)) => Huge(a, b, c, d)
  }

  implicit val hugeCaseClassReads: Reads[Huge] = (
    fields1to2 and fields3to4
  ) { f }

}