Quicklens

Modify deeply nested fields in case classes:

import com.softwaremill.quicklens._

case class Street(name: String)
case class Address(street: Street)
case class Person(address: Address, age: Int)

val person = Person(Address(Street("1 Functional Rd.")), 35)

val p2 = person.modify(_.address.street.name).using(_.toUpperCase)
val p3 = person.modify(_.address.street.name).setTo("3 OO Ln.")

// or
 
val p4 = modify(person)(_.address.street.name).using(_.toUpperCase)
val p5 = modify(person)(_.address.street.name).setTo("3 OO Ln.")

Chain modifications:

person
  .modify(_.address.street.name).using(_.toUpperCase)
  .modify(_.age).using(_ - 1)

Traverse options/lists using .each:

import com.softwaremill.quicklens._

case class Street(name: String)
case class Address(street: Option[Street])
case class Person(addresses: List[Address])

val person = Person(List(
  Address(Some(Street("1 Functional Rd."))),
  Address(Some(Street("2 Imperative Dr.")))
))

val p2 = person.modify(_.addresses.each.street.each.name).using(_.toUpperCase)

.each can only be used inside a modify and "unwraps" the container (currently supports Lists and Options). You can add support for your own containers by providing an implicit QuicklensFunctor[C] with the appropriate C type parameter.

Modify specific sequence elements using .at:

person.modify(_.addresses.at(2).street.each.name).using(_.toUpperCase)

Similarly to .each, .at modifies only the element at the given index. If there's no element at that index, an IndexOutOfBoundsException is thrown.

Re-usable modifications (lenses):

import com.softwaremill.quicklens._

val modifyStreetName = modify(_: Person)(_.address.street.name)

val p3 = modifyStreetName(person).using(_.toUpperCase)
val p4 = modifyStreetName(anotherPerson).using(_.toLowerCase)

//

val upperCaseStreetName = modify(_: Person)(_.address.street.name).using(_.toUpperCase)

val p5 = upperCaseStreetName(person)

Composing lenses:

import com.softwaremill.quicklens._

val modifyAddress = modify(_: Person)(_.address)
val modifyStreetName = modify(_: Address)(_.street.name)

val p6 = (modifyAddress andThenModify modifyStreetName)(person).using(_.toUpperCase)

---

Similar to lenses (1, 2), but without the actual lens creation.

Read the blog for more info.

Available in Maven Central:

val quicklens = "com.softwaremill.quicklens" %% "quicklens" % "1.4.1"

Also available for Scala.js!