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)

Implementing a CoreLocation wrapper as @ObservedObject

We mentioned in the introduction to this 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 if we want to bridge iOS foundation objects to the new SwiftUI model, such as CoreLocation functionalities. CoreLocation is the iOS framework...