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SwiftUI Cookbook

SwiftUI Cookbook

By : Giordano Scalzo, Nzokwe
4.3 (20)
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SwiftUI Cookbook

SwiftUI Cookbook

4.3 (20)
By: Giordano Scalzo, 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)
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Using @StateObject to preserve the model's life cycle

Even though it has solid foundations, SwiftUI is a relatively new framework. Apple adds new features in every release to adapt to the usage done by the community of developers.

In the first release of SwiftUI, @ObservedObject was provided to separate the model logic from the view logic. The usage that Apple was assuming was that the object would be injected from an external class, not created directly inside a View.

Creating an @ObserveObject in a View ties the life cycle of the object to the life cycle of the view.

However, the View can be destroyed and created several times while still appearing on the screen, where it should present the content of the view. When the View is destroyed, @ObservedObject is destroyed too, resetting its internal state.

This was a counter-intuitive behavior and most of the developers were assuming that @ObservedObject would keep its state until the owning view was shown on the screen...

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