Enabling Concurrency warnings in Xcode 14

Published on: September 13, 2022

If you want to make sure that your code adopts Swift concurrency as correctly as possible in Swift 5.7, it's a good idea to enable the Strict Concurrency Checking (SWIFT_STRICT_CONCURRENCY) in your project. To do this, select your project's target and navigate to the Build Settings tab. Make sure you select All from the list of settings that is shown (Basic is the default) and type Strict Concurrency in the searchbar to find the Strict Concurrency Checking build setting. The screenshot below shows all the relevant parts for you to see: The default value for this setting is Minimal which...

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What are Sendable and @Sendable closures in Swift?

Published on: September 13, 2022

One of the goals of the Swift team with Swift’s concurrency features is to provide a model that allows developer to write safe code by default. This means that there’s a lot of time and energy invested into making sure that the Swift compiler helps developers detect, and prevent whole classes of bugs and concurrency issues altogether. One of the features that helps you prevent data races (a common concurrency issue) comes in the form of actors which I’ve written about before. While actors are great when you want to synchronize access to some mutable state, they don’t solve every...

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Xcode 14 “Publishing changes from within view updates is not allowed, this will cause undefined behavior”

Published on: September 7, 2022

Dear reader, if you've found this page you're probably encountering the error from the post title. Let me start by saying this post does not offer you a quick fix. Instead, it serves to show you the instance where I ran into this issue in Xcode 14, and why I believe this issue is a bug and not an actual issue. I've last tested this with Xcode 14.0's Release Candidate. I've filed feedback with Apple, the feedback number is FB11278036 in case you want to duplicate my issue. Some of the SwiftUI code that I've been using fine for a...

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What are primary associated types in Swift 5.7?

Published on: June 8, 2022

Swift 5.7 introduces many new features that involve generics and protocols. In this post, we're going to explore an extremely powerful new features that's called "primary associated types". By the end of this post you will know and understand what primary associated types are, and why I think they are extremely important and powerful to help you write better code. If your familiar with Swift 5.6 or earlier, you might know that protocols with associated types have always been somewhat of an interesting beast. They were hard to use sometimes, and before Swift 5.1 we would always have to resort...

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What’s the difference between any and some in Swift 5.7?

Published on: June 8, 2022

Protocols are an extremely important part in the Swift language, and in recent updates we've received some new capabilities around protocol and generics that allow us to be much more intentional about how we use protocols in our code. This is done through the any and some keywords. In this post, you will learn everything you need to know about the similarities and differences between these two keywords. We'll start with an introduction of each keyword, and then you'll learn a bit more about the problems each keyword solves, and how you can decide whether you should use some or...

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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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Formatting dates in Swift using Date.FormatStyle on iOS 15

Published on: May 27, 2022

Formatting dates in Swift using Date.FormatStyle on iOS 15 Working with dates isn’t easy. And showing them to your users in the correct locale hasn’t always been easy either. With iOS 15, Apple introduced a new way to convert Date objects from and to String. This new way comes in the form of the new Formatter api that replaces DateFormatter. As any seasoned iOS developer will tell you, DateFormatter objects are expensive to create, and therefor kind of tedious to manage correctly. With the new Formatter api, we no longer need to work with DateFormatter. Instead, we can ask a...

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Closures in Swift explained

Published on: May 23, 2022

Closures are a powerful programming concept that enable many different programming patterns. However, for lots of beginning programmers, closures can be tricky to use and understand. This is especially true when closures are used in an asynchronous context. For example, when they’re used as completion handlers or if they’re passed around in an app so they can be called later. In this post, I will explain what closures are in Swift, how they work, and most importantly I will show you various examples of closures with increasing complexity. By the end of this post you will understand everything you need...

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Debugging Network Traffic With Proxyman

Published on: May 12, 2022

Disclaimer: This post is not sponsored by Proxyman, nor am I affiliated with Proxyman in any way. I pay for my license myself, and this post is simply written as a guide to learning more about a tool that I find very important in the iOS Developer toolbox. Networking is an essential part of modern iOS applications. Most apps I’ve worked have some kind of networking component. Sometimes the networking layer involves user authentication, token refresh flows, and more. Other times, I’ll simply need to hit one or two endpoints to fetch new data or configuration files for my app....

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The difference between checked and unsafe continuations in Swift

Published on: April 24, 2022

When you’re writing a conversion layer to transform your callback based code into code that supports async/await in Swift, you’ll typically find yourself using continuations. A continuation is a closure that you can call with the result of your asynchronous work. You have the option to pass it the output of your work, an object that conforms to Error, or you can pass it a Result. In this post, I won’t go in-depth on showing you how to convert your callback based code to async/await (you can refer to this post if you’re interested in learning more). Instead, I’d like...

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