A blog exploring functional programming and Swift.

Announcing Episode Collections

Wednesday Mar 11, 2020

After over two years and nearly 100 episodes we are finally launching episode collections on Point-Free!

Collections allow us to contextualize broad themes that we have covered on Point-Free, while also demonstrating that many of the seemingly disparate concepts are deeply connected in a beautiful way. Everything from parsing to randomness, and snapshot testing to composable architecture, all of these things are built on a common foundation of composition.

We have also redesigned our episode page (for example), which brings our episode videos front and center, and provides new ways of navigating to related content.

We hope that you enjoy these improvements to the site, and we have a lot more coming. If you have any feedback for us, please feel free to reach out.


Share Point-Free with friends and save!

Friday Feb 21, 2020

Today we’re excited to announce support for referral bonuses! When friends and colleagues of yours subscribe to Point-Free with your referral link, both of you will get one month free.

If you currently subscribe to Point-Free you can find your referral link on your account page.


Open Sourcing Case Paths

Tuesday Feb 4, 2020


Today we are open sourcing CasePaths, a library that introduces the power and ergonomics of key paths to enums!


We are excited to announce the 0.1.0 release of CasePaths, a new API that brings key path-like functionality and ergonomics to enums and unlocks the potential to write code that is generic over enums.

Motivation

Swift endows every struct and class property with a key path.

struct User {
  var id: Int
  var name: String
}

\User.id   // WritableKeyPath<User, Int>
\User.name // WritableKeyPath<User, String>

This is compiler-generated code that can be used to abstractly zoom in on part of a structure, inspect and even change it, while propagating these changes to the structure’s whole. They unlock the ability to do many things, like key-value observing and reactive bindings, dynamic member lookup, and scoping changes to the SwiftUI environment.

Unfortunately, no such structure exists for enum cases!

enum Authentication {
  case authenticated(accessToken: String)
  case unauthenticated
}

\Authentication.authenticated // 🛑

And so it’s impossible to write similar generic algorithms that can zoom in on a particular enum case.

Introducing: case paths

CasePaths intends to bridge this gap by introducing what we call “case paths.” Case paths can be constructed simply by prepending the enum type and case name with a forward slash:

import CasePaths

/Authentication.authenticated // CasePath<Authentication, String>

Case paths vs. key paths

While key paths package up the functionality of getting and setting a value on a root structure, case paths package up the functionality of extracting and embedding a value on a root enumeration.

user[keyPath: \User.id] = 42
user[keyPath: \User.id] // 42

let authentication = (/Authentication.authenticated).embed("cafebeef")
(/Authentication.authenticated).extract(from: authentication) // Optional("cafebeef")

Case path extraction can fail and return nil because the cases may not match up.

(/Authentication.authenticated).extract(from: .unauthenticated) // nil

Case paths, like key paths, compose. Where key paths use dot-syntax to dive deeper into a structure, case paths use a double-dot syntax:

\HighScore.user.name
// WritableKeyPath<HighScore, String>

/Result<Authentication, Error>..Authentication.authenticated
// CasePath<Result<Authentication, Error>, String>

Case paths, also like key paths, provide an “identity” path, which is useful for interacting with APIs that use key paths and case paths but you want to work with entire structure.

\User.self           // WritableKeyPath<User, User>
/Authentication.self // CasePath<Authentication, Authentication>

Key paths are created for every property, even computed ones, so what is the equivalent for case paths? “Computed” case paths can be created by providing custom embed and extract functions:

CasePath<Authentication, String>(
  embed: { decryptedToken in
    Authentication.authenticated(token: encrypt(decryptedToken))
  },
  extract: { authentication in
    guard
      case let .authenticated(encryptedToken) = authentication,
      let decryptedToken = decrypt(token)
      else { return nil }
    return decryptedToken
  }
)

Since Swift 5.2, key path expressions can be passed directly to methods like map. The same is true of case path expressions, which can be passed to methods like compactMap:

users.map(\User.name)
authentications.compactMap(/Authentication.authenticated)

Ergonomic associated value access

CasePaths uses Swift reflection to automatically and extract associated values from any enum in a single, short expression. This helpful utility is made available as a public module function that can be used in your own libraries and apps:

extract(case: Authentication.authenticated, from: .authenticated("cafebeef"))
// Optional("cafebeef")

Try it out today!

The official 0.1.0 release of CasePaths is on GitHub now, and we have more improvements and refinements coming soon. We hope that case paths will unlock all new kinds of interesting, expressive code! Try it today!


Older blog posts

Monday Dec 30, 2019

2019 Year-in-review

Random number generators, parsers, SwiftUI, composable architecture and more! Join us for a review of everything we accomplished in 2019!

Monday Dec 23, 2019

Snapshot Testing SwiftUI

Snapshot testing gives us broad test coverage on our SwiftUI views with very little up front work.

Wednesday Dec 18, 2019

Free Video: Testing SwiftUI

A free video exploring how to test SwiftUI.

Wednesday Nov 20, 2019

A Crash Course in Combine

Two free videos exploring Apple's new Combine framework, its core components, and how to integrate it in your code.

Thursday Nov 7, 2019

Higher-Order Snapshot Testing

How to enrich snapshot testing strategies with additional behavior using higher-order constructions.

Tuesday Jul 30, 2019

SwiftUI and State Management Corrections

Xcode 11 beta 5 has brought lots of changes to SwiftUI, and we'd like to take a moment to provide corrections to our episodes based on these changes.

Thursday May 9, 2019

Enterprise Subscriptions

Point-Free now supports enterprise subscriptions, making it easier than ever to manage a team subscription for larger organizations! For a fixed yearly rate, everyone with an email from your company's domain will get instant access to everything Point-Free has to offer. Contact us for more info!

Monday Apr 29, 2019

Open Sourcing Enum Properties

We wanted to make Swift enum data access as ergonomic as struct data access, so today we are open sourcing a code generation tool to do just that!

Monday Mar 18, 2019

Open Sourcing Gen

Today we are open sourcing Gen: a lightweight wrapper around Swift's randomness API's that makes randomess more composable, transformable and controllable!

Tuesday Jan 8, 2019

Announcing swift-html 0.2.0

Announcing swift-html 0.2.0: support for CocoaPods, Carthage, SnapshotTesting, and more!

Wednesday Dec 19, 2018

2018 Year-in-Review

41 episodes, 19 hours of video, 25 blog posts, 8 open source libraries, 3.8K stars, 36K visitors, and we’re just getting started?

Monday Dec 3, 2018

SnapshotTesting 1.0: Delightful Swift snapshot testing

Today we are open sourcing SnapshotTesting 1.0: a modern, composable snapshot testing library built entirely in Swift!

Monday Oct 29, 2018

Some news about contramap

We've seen that contramap is a powerful operation, but the name isn't fantastic. We propose a much more intuitive name for this operation, and in doing so make our code much easier to read.

Tuesday Oct 9, 2018

How to Control the World

APIs that interact with the outside world are unpredictable and make it difficult to test and simulate code paths in our apps. Existing solutions to this problem are verbose and complicated, so let's explore a simpler solution by embracing singletons and global mutation, and rejecting protocol-oriented programming and dependency injection.

Monday Oct 8, 2018

Watch episodes in your favorite podcast app!

Follow along with the newest Point-Free episodes using your favorite podcast app. We now support podcast-friendly RSS feeds for viewing all of our videos.

Thursday Sep 20, 2018

Random Zalgo Generator

Let's create a random Zalgo text generator using the simple Gen type we defined in this week's episode!

Thursday Sep 13, 2018

Type-safe HTML with Kitura

Today we're releasing a Kitura plug-in for rendering type-safe HTML. It provides a Swift compile-time API to HTML that prevents many of the runtime errors and vulnerabilities of traditional templated HTML rendering.

Thursday Sep 13, 2018

Type-safe HTML with Vapor

Today we're releasing a Vapor plug-in for rendering type-safe HTML. It provides a Swift compile-time API to HTML that prevents many of the runtime errors and vulnerabilities of traditional templated HTML rendering.

Wednesday Sep 12, 2018

Open sourcing swift-html: A Type-Safe Alternative to Templating Languages in Swift

Today we are open sourcing a new library for building HTML documents in Swift. It's extensible, transformable, type-safe, and provides many benefits over templating languages.

Friday Aug 17, 2018

Overture 0.3.0: Now with Zip

Today we are releasing Overture 0.3.0 with a bunch of useful zip functions.

Friday Aug 17, 2018

Open Sourcing Validated

Today we are open sourcing Validated, a tiny functional Swift library for handling multiple errors: functionality that you don't get from throwing functions and the Result type.

Thursday Aug 16, 2018

Solutions to Exercises: Zip Part 3

Today we solve the exercises to the third and final part of our introductory series on zip.

Wednesday Aug 15, 2018

Solutions to Exercises: Zip Part 2

Today we solve the exercises to the second part of our introductory series on zip.

Tuesday Aug 14, 2018

Solutions to Exercises: Zip Part 1

Today we solve the exercises to the first part of our introductory series on zip.

Monday Aug 6, 2018

Announcing Student Discounts

Get 50% off your Point-Free subscription with proof of enrollment at a university or coding school.

Monday Jul 30, 2018

Celebrating 6 Months

This week marks 6 months since our launch, and we’re making one of our most popular episodes free to the public!

Monday Jul 2, 2018

Conditional Coding

What happens when we combine Swift's conditional conformance with codability?

Monday Jun 25, 2018

Open Sourcing NonEmpty

Today we are open sourcing NonEmpty, a Swift library for modeling non-empty collection types. This small library can help make your code safer and more expressive with very little work.

Monday Jun 18, 2018

Tagged Seconds and Milliseconds

Let's create a type-safe interface for dealing with seconds and milliseconds in our programs. We'll use the `Tagged` type, which allows us to construct all new types in a lightweight way.

Wednesday May 30, 2018

Styling with Functions: Free for Everyone!

We are making one of our early episodes, “UIKit Styling with Functions”, free to everyone today! It’s a seminal episode that sets the foundation for some later work in the Point-Free series.

Tuesday May 15, 2018

Overture: Now with Functional Setters

Announcing Overture 0.2.0! This release is all about setters: functions that allow us to build complex transformations out of smaller units.

Monday May 7, 2018

Solutions to Exercises: Contravariance

This week we solve the exercises from our episode on contravariance, because there were _a lot_ of them!

Monday Apr 23, 2018

Case Study: Algebraic Data Types

Let’s look at a real world use for algebraic data types. We will refactor a data type that is used in the code on this very site so that the invalid states are unrepresentable by the compiler.

Monday Apr 23, 2018

Announcing Point-Free Pointers!

Today we are excited to announcement launch of Point-Free Pointers, a blog to supplement our video series for all the content we couldn’t fit in. Expect to find regularly postings here that dive even deeper into functional programming, showing real world use cases and more!