SwiftUI Background Tasks

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From the Materials repo, open the Starter folder under 03-background-tasks-made-easy.

Build and run the project. Tap Load Latest News, and you’ll see that the new version of the app now shows each article’s date. It’s a subtle but nice improvement.

If you prefer to continue with the project you developed in the previous lesson, please add the following files to it. If you started from the clean project in the Starter folder, these are the files you’ll work on in this lesson.

ArticleView.swift contains the SwiftUI view for a single article. It encapsulates the different views of the article to ease their management.

Now that the article has its own view, NewsView.swift has been updated to include this new SwiftUI component.

Last but not least, you need to update the Article.swift file to add the article date (publishedAt) and its corresponding decoding in the NewsService.swift. Be sure to set the correct date decoding strategy (.iso8601); otherwise, you’ll receive an error when decoding the list of articles.

Now you’re ready to rock ‘n’ roll.

AsyncImage

The first improvements you’ll make won’t add new features but will greatly simplify the code.

Triggering a Task on View Loading

Wouldn’t it be nice if the app started downloading the news upon startup without requiring the user to tap “Load Latest News”? You can incorporate a task which does that as soon as the view is on screen, to enhance the performance and user experience of a SwiftUI app significantly. You’ll use the .task { } modifier that executes the provided closure in the background when the view is loaded. In the background here signifies that the task is queued simultaneous to the view load, and none of them block each other.

Refreshing Views With Pull-to-Refresh

Now that you removed the button to load the latest news, you need to think about how the user can force a reload once the articles are already loaded.

Using onTapGesture

It’s now time for you to add a couple of subtle enhancements that will improve Apple News’s look, feel, and usability even more. You’ll allow the user to read any article thoroughly by opening it in the browser. You also want to add a title to the main window to make it look nicer.

Adding Persistence With an Actor

It’s time to add the last feature to Apple News to make it even more powerful. You’ll add a persistence layer to download the images to the phone’s storage so they can be reused later. For the sake of this lesson, you’ll add the download method, but reusing these images to provide a cache to Apple News isn’t too far off.

Introducing Swift Actors

In Swift concurrency, an actor is a new language feature that facilitates safe concurrent programming by preventing data races and ensuring exclusive access to a mutable state. An actor is a reference type (just like classes) that encapsulates a state protected by a concurrency context.

Implementing Persistence With an Actor

Create a new file named Persistence.swift, and add the Persistence actor:

Binding It All Together

You’ll modify the UI to have two buttons on the bottom right side of the article view — on the opposite side of the article’s date.

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