A Mapper object defines a mapping method map between two object types.

interface Mapper<in From, out To> {
fun map(from: From): To


val a : A
val mapper: Mapper<A,B> = MyA2BMapper()
val b : B =

Mapping Arrays & Dictionaries

Mapper has extensions to map values form arrays and dcitionaries:

fun <From, To> Mapper<From, To>.map(values: List<From>): List<To> = { ... }
fun <From, To, K> Mapper<From, To>.map(value: Map<K, From>): Map<K, To> { ... }

Default implementations

  • VoidMapper: Empty implementation that returns en error.
  • IdentityMapper<T>: Mapper that returns the same object.
  • CastMapper<In,Out>: Mapping by casting the object into the given types.
  • ClosureMapper<In,Out>: Mapper that has a closure/lambda upon initialization specifiying the mapping action.

Swift exclusive implementations

  • EncodableToDataMapper<T>: Encodable object to Data.
  • DataToDecodableMapper<T>: Data to a Decodable object.
  • EncodableToDecodableMapper<T>: Encodable object to a Decodable object.
  • NSCodingToDataMapper<T>: NSCoding object to Data.
  • DataToNSCodingMapper<T>: Data to a NSCoding object.

Creating custom mappers

Custom mappings must be created by subclassing or adopting the Mapper class/interface:

class MyA2BMapper : Mapper<A, B> {
override fun map(from: A): B = B(