为traits播放2.1 Json序列化?
我有这个:为traits播放2.1 Json序列化?,json,scala,playframework,playframework-2.1,Json,Scala,Playframework,Playframework 2.1,我有这个: package models import play.api.libs.json._ import play.api.libs.functional.syntax._ object ModelWrites { implicit val tmoWrites= Json.writes[TestModelObject] implicit val ihWrites = Json.writes[IntHolder] } case class TestModelObject
package models
import play.api.libs.json._
import play.api.libs.functional.syntax._
object ModelWrites {
implicit val tmoWrites= Json.writes[TestModelObject]
implicit val ihWrites = Json.writes[IntHolder]
}
case class TestModelObject(s1:String, s2:String)
case class IntHolder(i1:Int, i2:Int)
trait HasInts {
val ints: List[IntHolder]
}
当我这样做时:
scala> val tmo = new TestModelObject("hello", "world") with HasInts {
val ints = List(IntHolder(1,2), IntHolder(3,4))
}
scala> Json.toJson(tmo)
res0: play.api.libs.json.JsValue = {"s1":"hello","s2":"world"}
如何隐式序列化混合值“ints”?比如:
scala> val someInts = List(IntHolder(8,9), IntHolder(10,11))
someInts: List[models.IntHolder] = List(IntHolder(8,9), IntHolder(10,11))
scala> Json.toJson(someInts)
res1: play.api.libs.json.JsValue = [{"i1":8,"i2":9},{"i1":10,"i2":11}]
注意:如果我尝试:implicit val hasIntsWrites=Json.writes[HasInts]
I(预期?)得到:
您不能在这里直接使用(
Json.writes[…]
),因为这只适用于case类。然而,您可以在Inception提供的Writes
实例的基础上构建,只需一个非常小的样板就可以完成您想要的任务
请注意,我忽略了这样一个问题,即在实例化一个case类时,将trait混合在一起是否是一个好主意—可能不是—但我在这里给出的方法也适用于更一般的情况
首先是类和导入(此处无更改):
现在我们需要将所有低优先级实例放入trait中,以确保编译器选择正确的实例,因为带有HasInts的TestModelObject
是TestModelObject
和HasInts
的子类型:
trait LowPriorityWritesInstances {
implicit val tmoWrites = Json.writes[TestModelObject]
implicit val ihWrites = Json.writes[IntHolder]
implicit object hiWrites extends OWrites[HasInts] {
def writes(hi: HasInts) = Json.obj("ints" -> hi.ints)
}
}
现在的主要活动是:
object WritesInstances extends LowPriorityWritesInstances {
implicit val tmowhiWrites = new Writes[TestModelObject with HasInts] {
def writes(o: TestModelObject with HasInts) =
tmoWrites.writes(o) ++ implicitly[OWrites[HasInts]].writes(o)
}
}
我们完成了:
scala> import WritesInstances._
import WritesInstances._
scala> val tmo = new TestModelObject("hello", "world") with HasInts {
| val ints = List(IntHolder(1, 2), IntHolder(3, 4))
| }
scala> println(Json.toJson(tmo))
{"s1":"hello","s2":"world","ints":[{"i1":1,"i2":2},{"i1":3,"i2":4}]}
根据需要。棒极了。正是我想要的。谢谢!请注意,我忽略了这样一个问题,即在实例化一个case类时,将trait混入其中是否是一个好主意这可能不是“我洗耳恭听,如果你愿意解释的话:),现在我在猜测我自己。“案例到案例”继承很长一段时间以来一直被禁止,并且在2.10中被禁止,但是您在这里所做的(匿名从案例类继承)可能不会导致任何相同的问题。所以你可以忽略这一点。当我有几分钟的时间来检查更多细节时,我会尝试更新答案。
object WritesInstances extends LowPriorityWritesInstances {
implicit val tmowhiWrites = new Writes[TestModelObject with HasInts] {
def writes(o: TestModelObject with HasInts) =
tmoWrites.writes(o) ++ implicitly[OWrites[HasInts]].writes(o)
}
}
scala> import WritesInstances._
import WritesInstances._
scala> val tmo = new TestModelObject("hello", "world") with HasInts {
| val ints = List(IntHolder(1, 2), IntHolder(3, 4))
| }
scala> println(Json.toJson(tmo))
{"s1":"hello","s2":"world","ints":[{"i1":1,"i2":2},{"i1":3,"i2":4}]}