Unable to convert generic case class to json using “writes”

Question

I have a class which I want to be able to convert to json:

case class Page[T](items: Seq[T], pageIndex: Int, pageSize: Int, totalCount: Long)

object Page {

  i         


        

Answer 1

I don't think that you can have a generic writer for any type parameter. I propose following:

trait Page[T] {
  val items: Seq[T]
  val pageIndex: Int
  val pageSize: Int
  val totalCount: Long
}

case class IntPage(items: Seq[Int], pageIndex: Int, pageSize: Int, totalCount: Long) extends Page[Int]

object Page {
  implicit def jsonWriter = Json.writes[IntPage]
}