［Stack Overflow］ Play 和 Scala 的 地图ping 内容有数量限制吗

［Stack Overflow］ Play 和 Scala 的 mapping 内容有数量限制吗？
原文：http://stackoverflow.com/questions/11869990/mapping-error-with-the-play-frameworks-form



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我在使用 Play! framework 里的 mapping 时候遇到了问题。由于把mapping的参数改成一个的时候它运行的很好，所以我怀疑当我的mapping里的参数数量太大的时候他就罢工了，可是我在它的文档里没有找到任何关于这件事的内容：http://www.playframework.org/documentation/api/2.0.2/scala/index.html#play.api.data.Form

这是我的form的代码:

val paymentForm: Form[PaymentValues] = Form(// Define a mapping that will handle User valuesmapping(  "message" -> text,   "x_card_num" -> text,  "x_exp_date" -> text,  "exp_year" -> text,  "exp_month" -> text,  "x_card_code" -> text,  "x_first_name" -> text,  "x_last_name" -> text,  "x_address" -> text,  "x_city" -> text,  "x_state" -> text,  "x_zip" -> text,  "save_account" -> text,  "product_array" -> text,  "x_amount" -> text,  "products_json" -> text,  "auth_net_customer_profile_id" -> text,  "auth_net_payment_profile_id" -> text,  "customer_id" -> text,  "saved_payments_object" -> text )(PaymentValues.apply)(PaymentValues.unapply))

有没有什么方法可以把mapping分开吗？求教育。

下面是报错:

! Internal server error, for request [GET /] ->sbt.PlayExceptions$CompilationException: Compilation error [Overloaded method value [mapping] cannot be applied to  ((java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]), (java.lang.String, play.api.data.Mapping[String]))]at sbt.PlayReloader$$anon$2$$anonfun$reload$3$$anonfun$2$$anonfun$apply$11$$anonfun$apply$12.apply(PlayReloader.scala:224) ~[na:na]at sbt.PlayReloader$$anon$2$$anonfun$reload$3$$anonfun$2$$anonfun$apply$11$$anonfun$apply$12.apply(PlayReloader.scala:224) ~[na:na]at scala.Option.map(Option.scala:133) ~[scala-library.jar:0.11.2]at sbt.PlayReloader$$anon$2$$anonfun$reload$3$$anonfun$2$$anonfun$apply$11.apply(PlayReloader.scala:224) ~[na:na]at sbt.PlayReloader$$anon$2$$anonfun$reload$3$$anonfun$2$$anonfun$apply$11.apply(PlayReloader.scala:221) ~[na:na]at scala.Option.map(Option.scala:133) ~[scala-library.jar:0.11.2]

这里是参数的定义:

package models// definition of PaymentValuescase class PaymentValues(    message: String,    x_card_num: String,    x_exp_date: String,    exp_year: String,    exp_month: String,    x_card_code: String,    x_first_name: String,    x_last_name: String,    x_address: String,    x_city: String,    x_state: String,    x_zip: String,    save_account: String,    product_array: String,    x_amount: String,    products_json: String,    auth_net_customer_profile_id: String,    auth_net_payment_profile_id: String,    customer_id: String,    saved_payments_object: String)

forms scala playframework mapping playframework-2.0share|improve this questionedited Aug 10 '12 at 10:34Samuel
1,121211asked Aug 8 '12 at 17:31user687245
527 1 First of all, is PaymentValues a case class. If so, could you drop it in the question please? Because the problem should come from there. thanks – andy petrella Aug 8 '12 at 21:30 Hey Andy, I just updated with its definition. Thanks. – user687245 Aug 8 '12 at 23:043 Why not just do the refactor recommended here? stackoverflow.com/questions/11654992/… – Brian SmithAug 9 '12 at 14:561 Brian is right, you will probably need to refactor as the Form mapping API has a hard limit of 18 parameters (for reasons much like in Brian's link) – thatsmydoing Aug 9 '12 at 16:26

1 回答activeoldestvotesup vote1down voteaccepted

可以细读一下文档接口，Scala 和 Play 对 mapping 都是有参数数量限制的。

事实上，Play 用一个定义了数据绑定的类 ObjectMapping 代替了 mapping 。这个 ObjectMapping 类可以应用 apply 和 unapply 方法, domain object (对于 unapply来说) 和其他 20 多个参数组成构造参数。一共23个。

Scala 把所有的抽象类型 (tuples, functions, case classes, ...)的参数都限制在了22个 (看这里有证据)

这就是为什么Play不支持一个包含20个参数的mapping... (事实上据大量的留言说当有18个参数的时候他就不行了)

第二次编辑

如果你不相信我... 试试这个 ^^

import play.api.data._ import validation._import format._def mapping[R, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20](a1: (String, Mapping[A1]), a2: (String, Mapping[A2]), a3: (String, Mapping[A3]), a4: (String, Mapping[A4]), a5: (String, Mapping[A5]), a6: (String, Mapping[A6]), a7: (String, Mapping[A7]), a8: (String, Mapping[A8]), a9: (String, Mapping[A9]), a10: (String, Mapping[A10]), a11: (String, Mapping[A11]), a12: (String, Mapping[A12]), a13: (String, Mapping[A13]), a14: (String, Mapping[A14]), a15: (String, Mapping[A15]), a16: (String, Mapping[A16]), a17: (String, Mapping[A17]), a18: (String, Mapping[A18]), a19: (String, Mapping[A19]), a20: (String, Mapping[A20]))(apply: Function18[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, R])(unapply: Function1[R, Option[(A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20)]]): Mapping[R] = {  ObjectMapping20(apply, unapply, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20)}case class ObjectMapping20[R, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20](apply: Function20[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, R], unapply: Function1[R, Option[(A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20)]], f1: (String, Mapping[A1]), f2: (String, Mapping[A2]), f3: (String, Mapping[A3]), f4: (String, Mapping[A4]), f5: (String, Mapping[A5]), f6: (String, Mapping[A6]), f7: (String, Mapping[A7]), f8: (String, Mapping[A8]), f9: (String, Mapping[A9]), f10: (String, Mapping[A10]), f11: (String, Mapping[A11]), f12: (String, Mapping[A12]), f13: (String, Mapping[A13]), f14: (String, Mapping[A14]), f15: (String, Mapping[A15]), f16: (String, Mapping[A16]), f17: (String, Mapping[A17]), f18: (String, Mapping[A18]), f19: (String, Mapping[A19]), f20: (String, Mapping[A20]), val key: String = "", val constraints: Seq[Constraint[R]] = Nil) extends Mapping[R] with ObjectMapping {  val field1 = f1._2.withPrefix(f1._1).withPrefix(key)  val field2 = f2._2.withPrefix(f2._1).withPrefix(key)  val field3 = f3._2.withPrefix(f3._1).withPrefix(key)  val field4 = f4._2.withPrefix(f4._1).withPrefix(key)  val field5 = f5._2.withPrefix(f5._1).withPrefix(key)  val field6 = f6._2.withPrefix(f6._1).withPrefix(key)  val field7 = f7._2.withPrefix(f7._1).withPrefix(key)  val field8 = f8._2.withPrefix(f8._1).withPrefix(key)  val field9 = f9._2.withPrefix(f9._1).withPrefix(key)  val field10 = f10._2.withPrefix(f10._1).withPrefix(key)  val field11 = f11._2.withPrefix(f11._1).withPrefix(key)  val field12 = f12._2.withPrefix(f12._1).withPrefix(key)  val field13 = f13._2.withPrefix(f13._1).withPrefix(key)  val field14 = f14._2.withPrefix(f14._1).withPrefix(key)  val field15 = f15._2.withPrefix(f15._1).withPrefix(key)  val field16 = f16._2.withPrefix(f16._1).withPrefix(key)  val field17 = f17._2.withPrefix(f17._1).withPrefix(key)  val field18 = f18._2.withPrefix(f18._1).withPrefix(key)  val field19 = f19._2.withPrefix(f19._1).withPrefix(key)  val field20 = f20._2.withPrefix(f20._1).withPrefix(key)  def bind(data: Map[String, String]): Either[Seq[FormError], R] = {    merge(field1.bind(data), field2.bind(data), field3.bind(data), field4.bind(data), field5.bind(data), field6.bind(data), field7.bind(data), field8.bind(data), field9.bind(data), field10.bind(data), field11.bind(data), field12.bind(data), field13.bind(data), field14.bind(data), field15.bind(data), field16.bind(data), field17.bind(data), field18.bind(data), field19.bind(data), field20.bind(data)) match {      case Left(errors) => Left(errors)      case Right(values) => {        applyConstraints(apply(          values(0).asInstanceOf[A1],          values(1).asInstanceOf[A2],          values(2).asInstanceOf[A3],          values(3).asInstanceOf[A4],          values(4).asInstanceOf[A5],          values(5).asInstanceOf[A6],          values(6).asInstanceOf[A7],          values(7).asInstanceOf[A8],          values(8).asInstanceOf[A9],          values(9).asInstanceOf[A10],          values(10).asInstanceOf[A11],          values(11).asInstanceOf[A12],          values(12).asInstanceOf[A13],          values(13).asInstanceOf[A14],          values(14).asInstanceOf[A15],          values(15).asInstanceOf[A16],          values(16).asInstanceOf[A17],          values(17).asInstanceOf[A18],          values(18).asInstanceOf[A19],          values(19).asInstanceOf[A20]))      }    }  }  def unbind(value: R): (Map[String, String], Seq[FormError]) = {    unapply(value).map { fields =>      val (v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11, v12, v13, v14, v15, v16, v17, v18, v19, v20) = fields      val a1 = field1.unbind(v1)      val a2 = field2.unbind(v2)      val a3 = field3.unbind(v3)      val a4 = field4.unbind(v4)      val a5 = field5.unbind(v5)      val a6 = field6.unbind(v6)      val a7 = field7.unbind(v7)      val a8 = field8.unbind(v8)      val a9 = field9.unbind(v9)      val a10 = field10.unbind(v10)      val a11 = field11.unbind(v11)      val a12 = field12.unbind(v12)      val a13 = field13.unbind(v13)      val a14 = field14.unbind(v14)      val a15 = field15.unbind(v15)      val a16 = field16.unbind(v16)      val a17 = field17.unbind(v17)      val a18 = field18.unbind(v18)      val a19 = field19.unbind(v19)      val a20 = field20.unbind(v20)      (a1._1 ++ a2._1 ++ a3._1 ++ a4._1 ++ a5._1 ++ a6._1 ++ a7._1 ++ a8._1 ++ a9._1 ++ a10._1 ++ a11._1 ++ a12._1 ++ a13._1 ++ a14._1 ++ a15._1 ++ a16._1 ++ a17._1 ++ a18._1 ++ a19._1 ++ a20._1) ->        (a1._2 ++ a2._2 ++ a3._2 ++ a4._2 ++ a5._2 ++ a6._2 ++ a7._2 ++ a8._2 ++ a9._2 ++ a10._2 ++ a11._2 ++ a12._2 ++ a13._2 ++ a14._2 ++ a15._2 ++ a16._2 ++ a17._2 ++ a18._2 ++ a19._2 ++ a20._2)    }.getOrElse(Map.empty -> Seq(FormError(key, "unbind.failed")))  }  def withPrefix(prefix: String): ObjectMapping20[R, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20] = addPrefix(prefix).map(newKey => this.copy(key = newKey)).getOrElse(this)  def verifying(addConstraints: Constraint[R]*): ObjectMapping20[R, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20] = {    this.copy(constraints = constraints ++ addConstraints.toSeq)  }  val mappings = Seq(this) ++ field1.mappings ++ field2.mappings ++ field3.mappings ++ field4.mappings ++ field5.mappings ++ field6.mappings ++ field7.mappings ++ field8.mappings ++ field9.mappings ++ field10.mappings ++ field11.mappings ++ field12.mappings ++ field13.mappings ++ field14.mappings ++ field15.mappings ++ field16.mappings ++ field17.mappings ++ field18.mappings ++ field19.mappings ++ field20.mappings}

share|improve this answeredited Aug 9 '12 at 20:20
answered Aug 9 '12 at 20:07andy petrella
2,137516 Thanks for your research :). I followed Brian's suggestion to refactor and was able to fit it in haha. – user687245 Aug 9 '12 at 21:02 No problem... it's always interesting to understand (almost in play) why stuffs aren't done! Most of the time, it's because it is not possible ^^ – andy petrella Aug 9 '12 at 21:09

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