Combine: Asynchronous Programming With Swift

Learn all about declarative asynchronous programming with Swift using the Combine framework!

Writing asynchronous code can be challenging, with a variety of possible interfaces to represent, perform, and consume asynchronous work — delegates, notification center, KVO, closures, etc. Juggling all of these different mechanisms can be somewhat overwhelming. Does it really have to be this hard? Not anymore!

With Apple’s introduction of the Combine framework in WWDC 2019, declarative and reactive programming in Swift have become a meaningful aspect of the language and a game-changer in how developers perform and compose pieces of asynchronous work, making it a must-have tool at your disposal.

The introduction of Combine as a built-in framework in Apple’s ecosystem is promising news to developers who were interested in frameworks such as RxSwift or ReactiveSwift, but didn’t want the overhead of a third-party dependency. And while experience with either of the above is useful, it’s not a prerequisite for this book. You’ll learn everything from the ground up to become a true Combine master.

Combine is Apple’s framework to work with asynchronous events in a unified and reactive way that ensures your app is always up to date based on the latest state of its data.

What are these asynchronous events, you might ask? Anything that happens over time in your application can be represented by what is known as a Combine Publisher — network requests, user input, notifications, KVO, and much more. And since Combine unifies all of these different mechanisms under a single interface, this opens the door to interesting and powerful ways of composing logic and work in a declarative and universal way.