https://github.com/pathikrit/sauron

Yet another Scala lens macro
https://github.com/pathikrit/sauron

lenses scala scala-macros

Last synced: 22 days ago
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Yet another Scala lens macro

• Host: GitHub
• URL: https://github.com/pathikrit/sauron
• Owner: pathikrit
• Created: 2015-03-03T06:41:37.000Z (over 9 years ago)
• Default Branch: master
• Last Pushed: 2015-03-22T20:11:28.000Z (over 9 years ago)
• Last Synced: 2024-07-02T11:10:46.033Z (4 months ago)
• Topics: lenses, scala, scala-macros
• Language: Scala
• Homepage:
• Size: 343 KB
• Stars: 168
• Watchers: 12
• Forks: 11
• Open Issues: 2
• Metadata Files:
  • Readme: README.md

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README

        
Sauron [![Circle CI](https://img.shields.io/circleci/project/pathikrit/sauron.svg)](https://circleci.com/gh/pathikrit/sauron) [![Download](https://api.bintray.com/packages/pathikrit/maven/sauron/images/download.svg)](https://bintray.com/pathikrit/maven/sauron/_latestVersion)

--------

Lightweight [lens library](http://stackoverflow.com/questions/3900307/cleaner-way-to-update-nested-structures) in less than [50-lines of Scala](src/main/scala/com/github/pathikrit/sauron/package.scala):

```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:

```scala

person.copy(address = person.address.copy(

  street = person.address.street.copy(

    name = (person.address.street.name).toUpperCase)

  )

)

```

**Simple setters**:

```scala

lens(person)(_.address.street.name).setTo("1 Objective Rd.")

```

**Reusable lenses**:

```scala

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`:

```scala

val f = lens(_: Person)(_.address.street.name)

val p3: Person = f(p1)(_.toUpperCase)

val p4: Person = f(p2)(_.toLowerCase)

```

**Lens composition**:

```scala

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:

```scala

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](https://github.com/adamw/quicklens) library.