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)

Implementing a CoreLocation wrapper as @ObservedObject

We mentioned in the introduction to the chapter that @State is used when the state variable has value-type semantics. This is because any mutation of the property creates a new copy of the variable, which triggers a rendering of the view's body, but what about a property with reference semantics?

In this case, any mutation of the variable is applied to the variable itself and SwiftUI cannot detect the variation by itself.

In this case, we must use a different property wrapper, @ObservedObject, and the observed object must conform to ObservableObject. Furthermore, the properties of this object that will be observed in the view must be decorated with @Published. In this way, when the properties mutate, the view is notified, and the body is rendered again.

This will also help in case we want to bridge iOS foundation objects to the new SwiftUI model, such as CoreLocation functionalities. CoreLocation is the iOS framework...