Circe: 找不到 io.circe.generic.decoding.DerivedDecoder[A] 类型的惰性隐式值

创建于 2017-01-10 · 6评论 · 资料来源: circe/circe

这是我的情况
我有一些来自 finagle http get client 的 json ：

package com.hendisantika.circe

import cats.syntax.either._
import io.circe.{Decoder, Json}
import io.circe.optics.JsonPath._
import io.circe.parser._
import io.circe.generic.semiauto._

object TryCirce extends App {


  val json: String = """
    {
      "responseHeader":{
        "status":0,
        "QTime":1,
        "params":{
        "indent":"true",
        "q":"content_t:circe &&\narticle_id_l:6729941",
        "wt":"json"}},
      "response":{"numFound":1,"start":0,"docs":[
      {
        "id":"comment:9404033",
        "comment_id_l":9404033,
        "article_id_l":6729941,
        "reply_to_id_l":0,
        "user_id_l":1686628,
        "username_s":"uzumaki_naruto",
        "email_s":"[email protected]",
        "content_t":"Hello circe! I am learning about you now ",
        "report_i":0,
        "type_s":"comment",
        "category_is":[71],
        "category_ss":["JSON"],
        "created_dt":"2016-05-19T02:12:01Z",
        "created_ts_l":1463623921,
        "is_deleted_i":0,
        "country_code_s":"id",
        "_version_":1534721405555310592},
        {
        "id":"comment:14995036",
        "comment_id_l":14995036,
        "article_id_l":10169921,
        "reply_to_id_l":0,
        "user_id_l":1148579,
        "username_s":"uchiha_madara",
        "email_s":"[email protected]",
        "content_t":"Hai circe, You are very handsome.",
        "report_i":0,
        "type_s":"comment",
        "category_is":[71],
        "category_ss":["LIB"],
        "created_dt":"2017-01-10T01:28:51Z",
        "created_ts_l":1484011731,
        "is_deleted_i":0,
        "country_code_s":"id",
        "_version_":1556099467469389824}]
      }}"""


  implicit val comDecoder: Decoder[SolrDoc] = deriveDecoder[SolrDoc]


  val obj = decode[SolrDoc](json2) match {
    case Left(failure) => println("Oh no --> " + failure)
    case Right(com) => println("OK Success")
      println(com)
  }

}

case class SolrDoc(response: Option[SolrResponse])

case class SolrResponse(
                       numFound:Int,
                       start : Int,
                       docs : List[Article]
                       )

case class Article(
                        id: String,
                        comment_id_l: Option[Long],
                        article_id_l: Option[Long],
                        reply_to_id_l: Option[Long],
                        user_id_l: Option[Long],
                        username_s: Option[String],
                        email_s: Option[String],
                        content_t: String,
                        report_i: Option[Int],
                        type_s: Option[String],
                        category_is: List[Int],
                        category_ss: List[String],
                        created_dt: Option[String],
                        created_ts_l: Option[Long],
                        is_deleted_i: Option[Int],
                        country_code_s: Option[String],
                        version: Option[Long]
                      )

//Error:(43, 47) could not find Lazy implicit value of type io.circe.generic.decoding.DerivedDecoder[A]
  implicit val comDecoder: Decoder[SolrDoc] = deriveDecoder

// Error:(43, 47) not enough arguments for method deriveDecoder: (implicit decode: shapeless.Lazy[io.circe.generic.decoding.DerivedDecoder[A]])io.circe.Decoder[A].
Unspecified value parameter decode.
  implicit val comDecoder: Decoder[SolrDoc] = deriveDecoder

找不到 io.circe.generic.decoding.DerivedDecoder[A] 类型的惰性隐式值
```
我想将 JSON 对象解码为 scala 案例类对象
你有什么解决办法吗？
我也从谷歌阅读了关于 circe 的问题。
我如何解决这个问题。谢谢

资料来源

hendisantika

最有用的评论

半自动派生不会自动派生嵌套案例类的解码器。以下应该可以正常工作：

case class SolrDoc(response: SolrResponse)
case class SolrResponse(docs: Seq[Article])
case class Article()

object TryCirce extends App {
  import io.circe.Decoder
  import io.circe.generic.semiauto.deriveDecoder

  implicit val decodeArticle: Decoder[Article] = deriveDecoder[Article]
  implicit val decodeSolrResponse: Decoder[SolrResponse] = deriveDecoder[SolrResponse]
  implicit val decodeSolrDoc: Decoder[SolrDoc] = deriveDecoder[SolrDoc]
}

它也适用于真正的Article 。如果这不能解决您的问题，请重新打开。

travisbrown 于 2017-06-26

👍43 ❤1

所有6条评论

它与此免责声明有关吗？

hendisantika 于 2017-01-10

@hendisantika有这方面的消息吗？我也遇到了同样的错误。

0x5d 于 2017-05-25

👍2

嗨@castillobgr ，我还没有更新的消息。

hendisantika 于 2017-05-26

😕2

case class SolrDoc(response: SolrResponse)

case class SolrResponse(docs: Seq[Article])

case class Article()

object TryCirce extends App {


  import io.circe.generic.semiauto.deriveDecoder

  implicit val comDecoder: Decoder[SolrDoc] = deriveDecoder[SolrDoc]


}

 could not find Lazy implicit value of type io.circe.generic.decoding.DerivedDecoder[models.foo.SolrDoc]
[error]   implicit val comDecoder: Decoder[SolrDoc] = deriveDecoder[SolrDoc]

punkratz312 于 2017-06-12

👍4

半自动派生不会自动派生嵌套案例类的解码器。以下应该可以正常工作：

case class SolrDoc(response: SolrResponse)
case class SolrResponse(docs: Seq[Article])
case class Article()

object TryCirce extends App {
  import io.circe.Decoder
  import io.circe.generic.semiauto.deriveDecoder

  implicit val decodeArticle: Decoder[Article] = deriveDecoder[Article]
  implicit val decodeSolrResponse: Decoder[SolrResponse] = deriveDecoder[SolrResponse]
  implicit val decodeSolrDoc: Decoder[SolrDoc] = deriveDecoder[SolrDoc]
}

它也适用于真正的Article 。如果这不能解决您的问题，请重新打开。

travisbrown 于 2017-06-26

👍43 ❤1

@travisbrown我已将我的评论移至https://github.com/circe/circe/issues/386。这在我看来是更好的地方

punkratz312 于 2017-06-28

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Circe: 找不到 io.circe.generic.decoding.DerivedDecoder[A] 类型的惰性隐式值

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