[英]How to Decode a Generic Case Class with semiautomatic in Circe
I have the following case class:我有以下案例类:
case class QueryResult[T: Decoder](data: T)
It works with auto derivation.它适用于自动推导。
But I could not solve it to have a semiautomatic derivation.但是我无法解决它以进行半自动推导。
Here is my Test case:这是我的测试用例:
//import io.circe.generic.auto._ // with this it works
import io.circe.derivation._
case class Name(name: String)
case class QueryResult[T: Decoder](data: T)
implicit val nameDer = deriveDecoder[Name]
implicit def result[T: Decoder] = deriveDecoder[QueryResult[T]] // this does not work
This gives me:这给了我:
Error:(16, 50) No method evidence$1 in pme123.graphql.client.QueryResult[T] (this is probably because a constructor parameter isn't a val)
implicit def result[T: Decoder] = deriveDecoder[QueryResult[T]]
Which version of circe are you using?你用的是哪个版本的circe? In 0.12.3 I have to use import io.circe.generic.semiauto._
and the following works for me:在 0.12.3 我必须使用import io.circe.generic.semiauto._
并且以下对我import io.circe.generic.semiauto._
:
case class Name(name: String)
case class QueryResult[T: Decoder](data: T)
implicit val nameDer = deriveDecoder[Name]
implicit def result[T: Decoder] = deriveDecoder[QueryResult[T]]
val json = """{"data": {"name": "foo"}}"""
decode[QueryResult[Name]](json) // Right(QueryResult(Name(foo)))
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