# klenses

**Repository Path**: mirrors_andyglick/klenses

## Basic Information

- **Project Name**: klenses
- **Description**: Lenses for Kotlin
- **Primary Language**: Unknown
- **License**: Apache-2.0
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2022-02-28
- **Last Updated**: 2026-02-28

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# klenses
Lenses for Kotlin.

[![Maven Central](https://img.shields.io/maven-central/v/com.codepoetics/klenses.svg)](http://search.maven.org/#search%7Cga%7C1%7Cklenses)
[![Build Status](https://travis-ci.org/poetix/klenses.svg?branch=master)](https://travis-ci.org/poetix/klenses)

Lenses are property references with some extra abilities: they can also be used to create a copy of an object with the property set to a different value, and they compose to form pointers into nested objects.

```kotlin
data class Inner(val value: String)
data class Outer(val outerValue: String, val inner: Inner?)

val foo = Outer("foo", null)

val outerValueLens = +Outer::outerValue
val innerLens = Outer::inner orElse Inner("xyzzy")
val innerValueLens = innerLens + Inner::value 

assertEquals("foo", outerValueLens(foo))
assertEquals(Outer("quux", null), outerValueLens(foo, "quux"))
assertEquals(Inner("xyzzy"), innerLens(foo))
assertEquals(Outer("foo", Inner("frobnitz")), innerValueLens(foo, "frobnitz"))
assertEquals(Outer("foo", Inner("XYZZY")), innerValueLens(foo) { toUpperCase() })
```