Swift is the programming language Apple created for building apps on iPhone, iPad, and Mac. It replaced Objective-C, and today nearly every new iOS app is written in Swift. If you want to build an app for the App Store — or you own an iPhone and want to make something that runs on it — Swift is the language to learn.

How does Swift work? You write Swift code in Xcode, Apple's free development tool, and it compiles into a native app that runs directly on Apple devices. Swift is designed to be safe: its type system and optional handling catch many common mistakes before your app ever runs. With SwiftUI, Apple's modern framework, you describe what your interface should look like in code, and the system builds it for you — a text field, a button, and a list can be just a few lines each. You can also use UIKit, the older framework, for apps that need finer control.

Swift is a good fit for beginners because it reads almost like plain English.…