找不到FromRecord的隐式值

Question

我正在尝试使用avro & avro4s，但在运行一个愚蠢的示例时遇到了麻烦。

我甚至不能在源代码库中找到自己的测试版本来编译- https://github.com/sksamuel/avro4s/blob/master/avro4s-core/src/test/scala/com/sksamuel/avro4s/AvroJsonInputTest.scala#L14-L20

我得到了标题could not find implicit value for parameter fromRecord: com.sksamuel.avro4s.FromRecord[Foo]中提到的错误。

package test

import java.io.ByteArrayInputStream

import com.sksamuel.avro4s._
import org.specs2.mutable.Specification

class AvroSpec extends Specification {
  "My classes" should {
    "be deserialized by avro" in {
      case class Foo(num: Int, name: String)
      val json = """{ "num": 17, "name": "jibba-jabbba" }"""
      val inst = Foo(num = 17, name = "jibba-jabba")
      val in =  new ByteArrayInputStream(json.getBytes("UTF-8"), 0, json.length)
      val foo = new AvroJsonInputStream[Foo](in).iterator.toSet
      in.close()

      foo mustEqual Set(inst)
    }
  }
}

我使用的是Scala 2.11.8和avro 1.7.0。我做错了什么？

Answer 1

将case类声明移到方法定义之外：

package test

import java.io.ByteArrayInputStream

import com.sksamuel.avro4s._
import org.specs2.mutable.Specification

case class Foo(num: Int, name: String)
class AvroSpec extends Specification {
  "My classes" should {
    "be deserialized by avro" in {
      val json = """{ "num": 17, "name": "jibba-jabbba" }"""
      val inst = Foo(num = 17, name = "jibba-jabba")
      val in =  new ByteArrayInputStream(json.getBytes("UTF-8"), 0, json.length)
      val foo = new AvroJsonInputStream[Foo](in).iterator.toSet
      in.close()

      foo mustEqual Set(inst)
    }
  }
}