morphling

Class describing an optional property of a record that is always absent.

A prism between a base type containing the arguments required by a single constructor of a sum type, and that sum type, along with the schema for the base type is used to describe those constructor arguments. The identifier is used to distinguish which constructor is being represented in the serialized form.

Class describing a constant (non-serializable) property of a record.

Fixpoint data type that can preserve a type index through its recursive step.

Constructor that enables creation of schema for sum types.

Each constructor of the sum type I is represented as a member of the list of alternatives. Each alternative defines a prism between a single constructor of the sum type, and an underlying type describing the arguments demanded by that constructor.

Consider the following sum type. The first constructor takes no arguments; the second takes two.

sealed trait Role

case object User extends Role
case class Administrator(department: String, subordinateCount: Int) extends Role

A schema value for this type looks like:

val roleSchema = oneOf(
  alt[Unit, Prim, Role, Unit](
    "user",
    Schema.empty,
    (_: Unit) => User,
    {
      case User => Some(Unit)
      case _ => None
    }
  ) ::
  alt[Unit, Prim, Role, Administrator](
    "administrator",
    rec[Prim, Administrator](
      (
        required("department", Prim.str, (_: Administrator).department),
        required("subordinateCount", Prim.int, (_: Administrator).subordinateCount)
      ).mapN(Administrator.apply)
    ),
    identity,
    {
      case a @ Administrator(_, _) => Some(a)
      case _ => None
    }
  ) :: Nil
)

Class describing an optional property of a record. Since in many serialized forms optional properties may be omitted entirely from the serialized form, a distinct type is needed in order to be able to correctly interpret the absence of a field.

Schema constructor that wraps a value of an underlying GADT of allowed primitive types.

The underlying GADT defines a set of types via GADT constructors; see morphling.protocol.SType for an example. This set of types defines what types may be treated as primitive (and have parsing/ serialization/etc deferred to an external handler) when interpreting a schema value. For example, one might want to construct a GADT for for the Scala primitive types as such:

sealed trait SType[I]

case object SNullT   extends SType[Unit]
case object SBoolT   extends SType[Boolean]

case object SByteT   extends SType[Byte]
case object SShortT  extends SType[Short]
case object SIntT    extends SType[Int]
case object SLongT   extends SType[Long]

case object SFloatT  extends SType[Float]
case object SDoubleT extends SType[Double]

case object SCharT   extends SType[Char]
case object SStrT    extends SType[String]

This example treats String values as primitive as well, even though strictly speaking they're reference types, just because virtually any interpreter for a schema algebra will not want to represent strings in terms of sum or product types. The same might hold true for, for example, scala.Array but for the purposes of this example issues related to ClassManifest instances would introduce excessive complexity.

Base trait for values which describe record properties.

Wrapper for the free applicative structure which is used to construct and disassemble values of product types.

Class describing a required property of a record.

Data types and smart constructors which simplify the creation of schema values.

The base trait for the schema GADT.