Type Members

1.  trait JsonSchemas extends AnyRef

   An algebra interface for describing algebraic data types.

   An algebra interface for describing algebraic data types. Such descriptions can be interpreted to produce a JSON schema of the data type, a JSON encoder, a JSON decoder, etc.

   A description contains the fields of a case class and their type, and the constructor names of a sealed trait.

   For instance, consider the following record type:

   case class User(name: String, age: Int)

   Its description is the following:

   object User {
     implicit val schema: JsonSchema[User] = (
       field[String]("name") zip
       field[Int]("age")
     ).invmap((User.apply _).tupled)(Function.unlift(User.unapply))
   }

   The description says that the record type has two fields, the first one has type String and is named “name”, and the second one has type Int and name “age”.

   To describe sum types you have to explicitly “tag” each alternative:

   sealed trait Shape
   case class Circle(radius: Double) extends Shape
   case class Rectangle(width: Double, height: Double) extends Shape
   
   object Shape {
     implicit val schema: JsonSchema[Shape] = {
       val circleSchema = field[Double]("radius").invmap(Circle)(Function.unlift(Circle.unapply))
       val rectangleSchema = (
         field[Double]("width") zip
         field[Double]("height")
       ).invmap((Rectangle.apply _).tupled)(Function.unlift(Rectangle.unapply))
       (circleSchema.tagged("Circle") orElse rectangleSchema.tagged("Rectangle"))
         .invmap[Shape] {
           case Left(circle) => circle
           case Right(rect)  => rect
         } {
           case c: Circle    => Left(c)
           case r: Rectangle => Right(r)
         }
     }
   }