Lift JSON: How to convert convert list of tuples to JsonAST?

Question

The following code produces a List[JsonAst.JObject]:

val json = recommendations.map { r =>
  ("cardId" -> r._1) ~
  ("count" -> r._2)
}

This one doesn't. It produces List[(String, Int)]:

val json = recommendations.map { r =>
  (r._1.toString -> r._2)
}

How can I convert this List[(Int, Int)] into JSON?

Answer 1

For org.json4s.json library

Since (r._1.toString -> r._2) doesn't produce a JObject without the ~ operator, you need to lift it manually to JObject, which takes a list of Tuples as Parameter:

val json = recs.map { r =>
  JObject(List(JField(r._1, JInt(r._2))))
}

Produces:

List[JsonAST.JObject]

EDIT for net.liftweb.json library

val json = recs.map { r =>
  JObject(List(JField(r._1, JInt(r._2))))
}

EDIT Both libraries allow the same syntax