Lightweight lens library in less than 50-lines of Scala:
case class Person(address: Address)
case class Address(street: Street)
case class Street(name: String)
val person = Person(Address(Street("1 Functional Rd.")))
import com.github.pathikrit.sauron._
lens(person)(_.address.street.name)(_.toUpperCase)There is zero overhead; the lens macro simply expands to this during compilation:
person.copy(address = person.address.copy(
street = person.address.street.copy(
name = (person.address.street.name).toUpperCase)
)
)Simple setters:
lens(person)(_.address.street.name).setTo("1 Objective Rd.")Reusable lenses:
val f1 = lens(person)(_.address.street.name)
val p1: Person = f1(_.toLowerCase)
val p2: Person = f1(_.toUpperCase)Lens factories: The above lens only updates a particular person. You can make even more generic lenses that can update any Person:
val f = lens(_: Person)(_.address.street.name)
val p3: Person = f(p1)(_.toUpperCase)
val p4: Person = f(p2)(_.toLowerCase)Lens composition:
val lens1: Person ~~> Address = lens(_: Person)(_.address)
val lens2: Address ~~> String = lens(_: Address)(_.street.name)
val lens3: Person ~~> String = lens1 andThenLens lens2 // or lens2 composeLens lens1
val p5: Person = lens3(person)(_.toLowerCase)sbt: In your build.sbt, add the following entries:
resolvers += Resolver.bintrayRepo("pathikrit", "maven")
libraryDependencies += "com.github.pathikrit" %% "sauron" % "1.1.0"
addCompilerPlugin("org.scalamacros" % "paradise" % "2.1.0-M5" cross CrossVersion.full)This library is inspired by the clever work done by @adamw in his quicklens library.