尽管声明了隐式类型编译错误

Question

使用 org.json4s，我正在尝试编译此代码：

implicit val formats = org.json4s.DefaultJsonFormats
for {
  parsed <- Try(parse(message)).toOption
  purchase <- parsed.extractOpt[Item]
} yield {
  val datetime = new DateTime(purchase.time)
  val roundedTime = datetime.withMinuteOfHour(0).withSecondOfMinute(0).withMillisOfSecond(0)
  Key(purchase.item_id, roundedTime) -> purchase.amount
}

我收到以下错误：

"No org.json4s.Formats found. Try to bring an instance of org.json4s.Formats in scope or use the org.json4s.DefaultFormats."

Answer 1

你使用了错误的隐式。您需要使用 DefaultFormats 而不是 DefaultJsonFormats:

implicit val formats = org.json4s.DefaultFormats

尽管声明了隐式类型编译错误

Implicit type compilation error although declared

scala

scalatest

json4s