SwiftUI

Presenting a partially visible bottom sheet in SwiftUI on iOS 16

Published on: June 6, 2022

This post is up to date for Xcode 14.0 Beta 1 and iOS 16 Beta 1. It supersedes a version of this post that you can find here On iOS 15, Apple granted developers the ability to present partially visible bottom sheets using a component called UISheetPresentationController. Originally, we had to resort to using a UIHostingController to bring this component to SwiftUI. With iOS 16, we don't have to do this anymore. You can make use of the presentationDetents view modifier to configure your sheets to be fully visible, approximately half visible, or some custom fraction of the screen's height....

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Writing custom property wrappers for SwiftUI

Published on: January 16, 2022

It's been a while since I published my post that helps you wrap your head around Swift's property wrappers. Since then, I've done more and more SwiftUI related work and one challenge that I recently had to dig into was passing dependencies from SwiftUI's environment into a custom property wrapper. While figuring this out I learned about the DynamicProperty protocol which is a protocol that you can conform your property wrappers to. When your property wrapper conforms to the DynamicProperty protocol, your property wrapper will essentially become a part of your SwiftUI view. This means that your property wrapper can...

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Adding custom keys to the SwiftUI environment

Published on: January 10, 2022

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 app might have to do some date formatting, and maybe you’re looking for a...

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Understanding how and when SwiftUI decides to redraw views

Published on: November 7, 2021

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...

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Using UISheetPresentationController in SwiftUI 3

Published on: June 30, 2021

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,...

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Fetching objects from Core Data in a SwiftUI project

Published on: August 10, 2020

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...

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Using Core Data with SwiftUI 2.0 and Xcode 12

Published on: July 20, 2020

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...

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Handling deeplinks in iOS 14 with onOpenURL

Published on: July 6, 2020

Starting with iOS 14, we can write apps that are fully built using SwiftUI, dropping the need to have AppDelegate and SceneDelegate files entirely. For as long as I remember, I've handled deeplinks in my AppDelegate and for the past year in the SceneDelegate. So when Apple introduced developers to this new @main annotated App struct style of building apps, I'm sure we all had the same question on our mind. How does the new App struct work with deeplinks and other tasks that are normally performed in the AppDelegate? Luckily, Apple engineers made sure that handling deeplinks in our...

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Implementing an infinite scrolling list with SwiftUI and Combine

Published on: June 29, 2020

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...

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Using multi-colored icons in iOS 14 with SF Symbols 2

Published on: June 28, 2020

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...

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