Combine: Asynchronous Programming with Swift

Introduction

The book «Combine: Asynchronous Programming with Swift» by the Raywenderlich Tutorial Team is arguably one of the best practical guides to the Combine framework, introduced by Apple in 2019. Published in 2021, it spans 472 pages and is aimed at iOS and macOS developers proficient in Swift. Unlike dry documentation, this book offers a step-by-step exploration of reactive programming through real-world projects and exercises.

What is this book about?

The book is dedicated to the Combine framework, which allows handling asynchronous events (network requests, user input, notifications) through a unified interface of Publishers, Subscribers, and Operators. The authors progressively reveal concepts from simple to complex: from basic subscriptions to creating custom operators and integrating with SwiftUI. Each chapter contains a practical assignment that reinforces the theory.

Who is this book for?

The book is intended for Swift developers already familiar with the basics of the language and the Apple platform. Beginners in asynchronous programming may find it challenging, but with basic knowledge of closures and protocols, the material becomes accessible. The book is especially useful for those transitioning from UIKit to SwiftUI, where Combine plays a key role.

What will the reader learn?

• Combine Basics: what Publisher, Subscriber, and Subscription are and how they interact.
• Operators: map, filter, merge, combineLatest, flatMap, and dozens of others for transforming data streams.
• Memory Management: how to avoid leaks using AnyCancellable and Scheduler.
• Error Handling: tryMap, catch, retry, and failure recovery strategies.
• Integration with UIKit and SwiftUI: linking Combine with ObservableObject, @Published, and @State.
• Testing: writing tests for Combine code using XCTestExpectation.
• Advanced Topics: creating custom operators, working with KVO and NotificationCenter.

Strengths of the book

The first thing that stands out is the structure. The book is divided into 5 parts: introduction, basics, advanced operators, integration with UIKit/SwiftUI, and a final project. Each chapter contains clear goals, code with explanations, and assignments for independent work. The second is the focus on real-world scenarios: you don't just read theory, but write a recipe search app, a chat client, and a weather widget. The third is the quality of editing: all examples are tested for compatibility with Xcode 12 and Swift 5.3, ensuring the code works.

Who is it recommended for

The book will be useful for iOS developers of any level who want to master a modern approach to asynchronicity. I especially recommend it to those who are tired of callbacks and delegates and want to write cleaner, more predictable code. If you plan to use SwiftUI in production, Combine will become your indispensable tool, and this book will help you master it quickly and painlessly.