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)

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 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, such as in 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, meaning that 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 the user...