In Xcode 16, it's possible to add custom keys using the convenient @Entry macro. Sometimes you’ll find yourself in a situation where you want to conveniently pass some object down via the SwiftUI environment. An easy way to do this is through the .environmentObject view modifier. The one downside of this view modifier and corresponding @EnvironmentObject property wrapper is that the object you add to the environment must be an observable object. Luckily, we can extend the SwiftUI environment to add our own objects to the @Environment property wrapper without the need to make these objects observable. For example, your...

There's a good chance that you're using SwiftUI and that you're not quite sure how and when SwiftUI determines which views should redraw. And arguably, that's a good thing. SwiftUI is clearly smart enough to make decent decisions without any negative consequences. In fact, you might even have set up your app in a way that coincidentally plays into SwiftUI's strength beautifully. There's an equal likelihood that your setup isn't as performant as you might think but you're just not seeing any issues yet. Recently, I had to figure out how SwiftUI determines that it should redraw views in order...

This post applies to the version of SwiftUI that shipped with iOS 15, also known as Swift 3. To learn how you can present a bottom sheet on iOS 16 and newer, take a look at this post. With iOS 15, Apple introduced the ability to easily implement a bottom sheet with UISheetPresentationController in UIKit. Unfortunately, Apple didn't extend this functionality to SwiftUI just yet (I'm hoping one of the iOS 15 betas adds this...) but luckily we can make use of UIHostingController and UIViewRepresentable to work around this limitation and use a bottom sheet on SwiftUI. In this post,...

When you've added Core Data to your SwiftUI project and you have some data stored in your database, the next hurdle is to somehow fetch that data from your Core Data store and present it to the user. In this week's post, I will present two different ways that you can use to retrieve data from Core Data and present it in your SwiftUI application. By the end of this post you will be able to: Fetch data using the @FetchRequest property wrapper Expose data to your SwiftUI views with an observable object and an @Published property. Since @FetchRequest is...

In Xcode 12 you can create projects that no longer use an AppDelegate and SceneDelegate to manage the application lifecycle. Instead, we can use Swift's new @main annotation to turn a struct that conforms to the App protocol into the main entry point for our applications. When you create a new project in Xcode 12, you have the option to use the SwiftUI App application lifecycle for your SwiftUI project. While Xcode 12 beta 5 introduces an option to include Core Data in your SwiftUI application when you create a new project, you might have an existing SwiftUI project that...

The quickest way to handle deeplinks in your app is through the onOpenURL(perform:) view modifier which has been available since iOS 14. It allows developers to register a URL handler on their views so they can respond to URLs by modifying state for their views as needed. In this post, we'll cover all the steps involved in setting up your app to handle deeplinks. We'll start with explaining what deeplinks are, and then we'll configure an Xcode project to allow your app to handle incoming deeplinks. Note that we won't cover setting up Universal Links in this post; we'll solely...

Tons of apps that we build feature lists. Sometimes we build lists of settings, lists of todo items, lists of our favorite pictures, lists of tweets, and many other things. Some of these lists could scroll almost endlessly. Think of a Twitter timeline, a Facebook feed or a list of posts on Reddit. You might argue that knowing how to build a list that scrolls infinitely and fetches new content whenever a user reaches the end of the list is an essential skill of any iOS developer. That's why as one of my first posts that covers SwiftUI I wanted...

Apple introduced SF Symbols in iOS 13. SF Symbols allow developers to easily integrate icons in their apps. The SF Symbols icons integrate really well with the default system font, and provide a consistent look throughout the system. In iOS 14, Apple added over 750 new icons to the SF Symbols library for developers to use in their apps. Additionally, Apple has expanded SF Symbols to include multi-colored icons. For a full overview of the available SF Symbols that are available, including the newly added and multicolor symbols, download the SF Symbols 2 app from Apple's SF Symbols page. To...

Views in SwiftUI are thrown away and recreated regularly. When this happens, the entire view struct is initialized all over again. Because of this, any values that you create in a SwiftUI view are reset to their default values unless you've marked these values using @State. This means that if you declare a view that creates its own @ObservedObject instance, that instance is replaced every time SwiftUI decides that it needs to discard and redraw that view. If you want to see what I mean, try running the following SwiftUI view: class DataSource: ObservableObject { @Published var counter = 0...

In SwiftUI, views can be driven by an @Published property that's part of an ObservableObject. If you've used SwiftUI and @Published before, following code should look somewhat familiar to you: class DataSource: ObservableObject { @Published var names = [String]() } struct NamesList: View { @ObservedObject var dataSource: DataSource var body: some View { List(dataSource.names, id: \.self) { name in Text(name) } } } Whenever the DataSource object's names array changes, NamesList will be automatically redrawn. That's great. Now imagine that our list of names is retrieved through the network somehow and we want to load the list of names in...