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)

Filtering Core Data requests using a predicate

An essential characteristic of Core Data is the possibility of filtering the results of a @FetchRequest so that only the objects that match a filter are retrieved from the repository and transformed into actual objects.

A predicate is a condition that the Core Data objects must satisfy to be fetched; for example, the name must be shorter than 5 characters, or the age of a person should be greater than 18. The conditions in a predicate can also be composite; for example, fetch all the data where the name is equal to "Lewis" and the age is greater than 18.

Even though the property wrapper accepts NSPredicate, which is a filter for Core Data, the problem is that this cannot be dynamic, which means it must be created at the beginning. It cannot change during the life cycle of the view as a result of a search text field, for example.

In this recipe, we'll learn how to create a dynamic filter for a contact list, where...