Book Image

SwiftUI Cookbook

By : Giordano Scalzo, Edgar Nzokwe
Book Image

SwiftUI Cookbook

By: Giordano Scalzo, Edgar Nzokwe

Overview of this book

SwiftUI is an innovative and simple way to build beautiful user interfaces (UIs) for all Apple platforms, right from iOS and macOS through to watchOS and tvOS, using the Swift programming language. In this recipe-based book, you’ll work with SwiftUI and explore a range of essential techniques and concepts that will help you through the development process. The recipes cover the foundations of SwiftUI as well as the new SwiftUI 2.0 features introduced in iOS 14. Other recipes will help you to make some of the new SwiftUI 2.0 components backward-compatible with iOS 13, such as the Map View or the Sign in with Apple View. The cookbook begins by explaining how to use basic SwiftUI components. Then, you’ll learn the core concepts of UI development such as Views, Controls, Lists, and ScrollViews using practical implementation in Swift. By learning drawings, built-in shapes, and adding animations and transitions, you’ll discover how to add useful features to the SwiftUI. When you’re ready, 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 while 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 found in building SwiftUI apps.
Table of Contents (15 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 new feature of Swift 5.1, the function builders, to create an extension to the 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 StopWatchApp.

How to do it…

The goal of the app is to have a stopwatch that can be started and stopped using a button. We are going to implement the counter using three...