Book Image

SwiftUI Cookbook - Second Edition

By : Giordano Scalzo, Edgar Nzokwe
Book Image

SwiftUI Cookbook - Second Edition

By: Giordano Scalzo, Edgar Nzokwe

Overview of this book

SwiftUI provides an innovative and simple way to build beautiful user interfaces (UIs) for all Apple platforms, from iOS and macOS through to watchOS and tvOS, using the Swift programming language. In this recipe-based cookbook, you’ll cover the foundations of SwiftUI as well as the new SwiftUI 3 features introduced in iOS 15 and explore a range of essential techniques and concepts that will help you through the development process. The cookbook begins by explaining how to use basic SwiftUI components. Once you’ve learned the core concepts of UI development, such as Views, Controls, Lists, and ScrollViews, using practical implementations in Swift, you'll advance to adding useful features to SwiftUI using drawings, built-in shapes, animations, and transitions. You’ll understand how to integrate SwiftUI with exciting new components in the Apple development ecosystem, such as Combine for managing events and Core Data for managing app data. Finally, you’ll write iOS, macOS, and watchOS apps by sharing the same SwiftUI codebase. By the end of this SwiftUI book, you'll have discovered a range of simple, direct solutions to common problems encountered when building SwiftUI apps.
Table of Contents (17 chapters)

Managing the memory in Combine to build a timer app

When a client subscribes to a publisher, the result should be held somewhere. Usually, it is stored in a Set of AnyCancellable. If the client subscribes to multiple publishers, the code is a bit repetitive: it would be better to have a way to wrap all subscriptions and put all the results in the same set.

In this recipe, we'll use a feature that was experimentally introduced in Swift 5.1 that was then promoted as part of the language in Swift 5.4, the result builders, to create an extension of Set of AnyCancellable, wrap all the subscriptions, and store them in the set.

In this recipe, we are going to create a StopWatch app using three publishers: one for the deciseconds, one for the seconds, and one for the minutes.

We will also learn how to use timers in Combine.

Getting ready

Let's create a SwiftUI app called StopWatch.

How to do it…

The goal of the app is to have a stopwatch that can be started...