The Case of the Vanishing Bodies

An Introduction to Swift Macros

by Daniel H Steinberg

The Case of the Vanishing Bodies is an introduction to the magic of freestanding and attached Swift Macros. You’ll learn to create a variety of macros. You’ll get a feel for when you should and shouldn’t create them, which sort of macro you should create, and how to use SwiftSyntax to implement them.

This work was written and produced entirely by the author. We are proud to be distributing it.

The Case of the Vanishing Bodies is an introduction to the magic of freestanding and attached Swift Macros.

There’s a fair amount of boilerplate code involved in so many of our everyday tasks as Swift programmers. Until Xcode 15, every time we created a new SwiftUI View we had to create the corresponding preview code. The struct and computed property weren’t interesting in any way - they were just a necessary task we needed to perform to display a preview of our View. With the introduction of the #Preview macro, we now only need to provide the code required to create an instance of the view being displayed.

In this book you’ll learn to create a variety of macros. You’ll get a feel for when you should and shouldn’t create them, which sort of macro you should create, and how to use SwiftSyntax to implement them. Your macros will accept parameters when appropriate and will always include tests. You’ll even learn to create helpful diagnostics for your macros and even FixIts.

You will need a Mac running the Xcode 15 or above.

Source code, Errata, Typos, Suggestions

Releases:

• P1.0 2024/07/31

Prelude: Before we Begin

Chapter 1: A Look Around excerpt

• Perhaps we can give it a try
• Tale of Two Macros
• The Model Macro
• The Xcode Macro Template
• Road Map
• Credits

Chapter 2: Our First Macro

• Naming the Macro
• Defining the Macro
• Passing Tests
• Adding a Second Parameter
• Manipulating Strings
• Accessing Values Using ASTs
• Introducing SwiftSyntax

Chapter 3: Freestanding Macros excerpt

• URL: You do it
• Throwing Errors
• Using Macros in Projects
• Using Macros in Macros
• Declaration Macros
• Helper Methods
• Diagnostics

Chapter 4: Our First Attached Macro

• Explaining our goal
• Seeing is not believing
• Introducing an Attached Macro
• Parameters for Expanding
• Adding Flexibility to our Macro
• More Diagnostics
• FixIts

Chapter 5: More Attached Macros excerpt

• Macros and the Three Bears
• Extension Macros
• Accessor Macros
• Peer Macros
• Identifying Stored Properties
• Combining Macros
• MemberAttribute Macros
• Presenting Macros in Macros

Daniel H Steinberg is the author of more than a dozen books including the best selling books A Functional Programming Kickstart, A Swift Kickstart, Second Edition and Dear Elena. He has written apps for the iPhone and the iPad since the SDKs first appeared and has written programs for the Mac all the way back to System 7.

Daniel presents iOS, Functional Programming, SwiftUI, and Swift training and consults through his company Dim Sum Thinking. When he’s not coding or talking about coding for the Mac, the iPhone, and the iPad he’s probably cooking, baking bread, or hanging out with friends. Details on his training and speaking are on the Dim Sum Thinking website.