Did you know that Xcode can spell check your code and comments? Based on my experience working on large teams and large Xcode projects, this is a little-known feature. I routinely find spelling errors, not only in code comments but in symbol names. For the latter, this is particularly frustrating when a misspelled symbol is widely used because correcting that error — a rename that affects a substantial portion of the codebase — produces a large diff. Once you notice that your entire team has been passing around a “databaesQuery” for six months, it will drive you insane until fixed.

Continue…

Type erasure is a method to abstract and encapsulate heterogenous generic types inside a single non-generic concrete type. In programming languages with generic types, this is a mechanism for runtime polymorphism which allows you circumvent the constraints of generics at compile time. In the early days of Swift, generics were more challenging to work with — in particular, protocols with associated types. As of Swift 5.7 (and SE-0309: Unlock existentials for all protocols), type erasure is now a feature of the Swift compiler. However, there are still situations where you may need to manually write your own type-erased wrappers.

Continue…

UIKit provides two diffable data source APIs, one for collections and one for tables. Recently, while working on ReactiveCollectionKit, I noticed that the APIs were updated for Swift Concurrency in the iOS 18 SDK, but the annotations were inconsistent with the documentation.

Continue…

Welcome to the next post in my series about ReactiveCollectionsKit. Today I want to discuss diffing. Understanding diffing requires understanding two core concepts: identity and equality. These are two ideas that are also relevant and applicable to programming in general, and can often be confusing for newcomers.

Continue…

I recently released a new open source project called ReactiveCollectionsKit. It is a modern, fast, and flexible library for building data-driven, declarative, reactive, and diffable collections and lists for iOS. This library is the culmination of everything I learned from building and maintaining IGListKit, ReactiveLists, and JSQDataSourcesKit. The 4th time’s a charm! 😅 🍀 I truly hope this is the last UICollectionView library I ever write and maintain. I think it will be. You can find the documentation here.

Continue…

SwiftUI’s new @Observable macro is not a drop-in replacement for ObservableObject. I learned of a subtle difference in behavior the hard way. Hopefully, I can save you from the same headache I experienced and save you some time.

Continue…

While the new Swift Testing framework announced this year at WWDC24 is getting a lot of attention, there are some notable improvements coming to UI testing in XCTest in Xcode 16.

Continue…

I previously wrote about how the requirements for screenshots on the App Store have become increasingly burdensome over the years. It is truly a nightmare. But today I have good news to share! Our nightmare is coming to an end, as changes to screenshot requirements were announced at WWDC24 this year.

Continue…

SwiftUI introduced the ScenePhase API in iOS 14 and macOS 11. This was SwiftUI’s answer to handling application lifecycle events. At the same time, SwiftUI introduced UIApplicationDelegateAdaptor for iOS and NSApplicationDelegateAdaptor for macOS, which allow you to provide an AppDelegate on both platforms to receive additional application lifecycle events and other events that were missing from SwiftUI at the time. Unfortunately, many of those application event APIs are still missing and ScenePhase has a number of bugs (or at least, unexpected behavior).

Continue…

If you have attempted to adopt Swift Concurrency in your codebase, you have certainly needed to address dozens — likely, hundreds — of warnings and errors. Sometimes the issues can be resolved by addressing them directly. That is, your code was incorrect and you simply have to fix it to make it correct. In other scenarios, the resolution is not so straightforward. In particular, it is difficult to satisfy the compiler when working with APIs that you do not own that have not been updated for concurrency. Or, you may have found yourself in a situation where you know your code is correct, but the compiler is unable to verify its correctness — either because of a few remaining bugs in Swift Concurrency, or because you are using @preconcurrency APIs.

Continue…

More and more Apple Platform developers are migrating away from CocoaPods in favor the Swift Package Manager, which is Apple’s first-party tool for managing and integrating dependencies. While it is still not quite a complete replacement for CocoaPods, it is getting closer. Unfortunately, SwiftPM’s integration with Xcode still has a number of shortcomings, even though it was introduced with Xcode 11 — 4 years ago. The worst bug is that Xcode frequently and randomly deletes the Package.resolved, which in turn produces dozens or hundreds of 'missing package product' errors. Here’s how I’ve worked around this bug on a team I work on.

Continue…

At last year’s WWDC, Apple introduced privacy manifests. They recently sent out a reminder that the deadline for complying with these new requirements is May 1. Privacy manifests expand on the previously introduced privacy “nutrition labels” that are self-reported by developers and displayed on the App Store. Developers must start including a privacy manifest in their apps by the aforementioned deadline, but what’s more interesting is that Apple is, for the first time, imposing these new privacy rules on third-party SDKs as well. Even more interesting is the list of SDKs that Apple has published, which, upon inspection is quite bizarre.

Continue…

On macOS 14 Sonoma there is a regression in Swift 5.9 which causes Swift scripts that import Cocoa frameworks to fail. This issue was first reported by @rdj. I discovered it myself shortly after. There is a ticket open at #68785 on the main Swift repo on GitHub to track the issue.

Continue…

I recently setup fastlane for one of my indie apps, Taxatio, to automate uploading builds and metadata to the App Store — by far, one of the most tedious tasks of app development. While I had used fastlane extensively before when working on teams at companies, I had never actually set it up from scratch. In this post, I want to share how to do that, as well as a lightweight configuration that I think works well for solo indie developers — folks on a team of one!

Continue…

My Mac menu bar apps, Red Eye and Lucifer, are now for sale on my new Gumroad store.

Continue…

Perhaps “quirks” is not the correct description, but I recently encountered some unexpected behavior when modifying a protocol in Swift. While I was initially slightly confused, how Swift handles protocol requirements does make sense — conformances are more lenient than you might think!

Continue…

Providing screenshots for the App Store has always been a tedious and time-consuming process. But as the number of differently-sized iOS devices has grown and changed over the years, it has become more difficult to manage. (This is why the developer community built tools like fastlane snapshot.) The screenshot requirements for the App Store have increasingly become a burden for developers, especially indies. With the Mac App Store, there are fewer hurdles and less strict requirements. However, if you are now targeting only the latest OS releases and latest hardware, the screenshot requirements for both App Stores are not only burdensome but they no longer makes any sense!

Continue…

While working on updating iOS screenshots for the App Store recently, I discovered that simctl status_bar is still broken. And unfortunately, I do not expect it to be fixed any time soon.

Continue…

I’m happy to share that I released an update to Taxatio today, but unfortunately it was not without a lot of friction and hassle with the App Store approval process.

Continue…

I recently discovered, while setting up my first Apple Silicon Mac, that Xcode does not have access to your shell environment. But there’s one caveat to that. (Thanks to Boris for confirming!) This post will hopefully be a reminder to my future self when I encounter this issue again.

Continue…

After setting up my new M3 MacBook Pro, I decided to do some quick performance comparisons with my old Intel machine. Anecdotally, I would have told you that it is insanely faster but seeing the data made my jaw drop.

Continue…

A few weeks ago my AirPods Pro 2 (with Lightning, not USB-C) suddenly started acting buggy and weird. The case no longer made the chime sound when plugging them in to charge. I stopped getting “Left Behind” notifications from the Find My app. After updating to iOS 17, I could not get them to install the latest firmware, which enables the new features for Adaptive Audio, Conversation Awareness, and Personalized Volume. I had been trying for weeks to follow the magic steps that will trigger a firmware update with no luck. Even worse, after a full charge of both the AirPods and the case, the batteries for all of them would drain to zero percent within 2-3 days.

Continue…

When you work on a large team and are participating in many pull requests on GitHub, it can be difficult to keep track of everything you are working on. In addition to opening your own pull requests, you can be assigned to them, you can be requested as a reviewer, you can comment in discussion threads, and you can be mentioned by others. Each of these occurrences requires your attention — perhaps immediately, but always eventually.

Continue…

Foundation’s URL (née NSURL) is a nearly ubiquitous API on Apple platforms. One of its shortcomings is that it is heavily overloaded – an instance of URL could represent a web URL or a file URL. While there are many similarities between accessing resources on a local disk or on a web server, I think there should be explicit types for each, say WebURL and FileURL.

Continue…

In UIKit, UITableViewCell has a customizable accessory view. You can use one of the few accessory options that is provided by iOS by setting the accessoryType property, or you can provide a custom view using accessoryView, which can be any UIView. The equivalent of constructing a UITableViewCell with a chevron accessory in SwiftUI is using a NavigationLink. Unfortunately, however, SwiftUI does not provide an API to customize the accessory view for a NavigationLink — you are stuck with the default chevron.

Continue…

UserDefaults is probably one of the most popular APIs on Apple Platforms. It is a highly-optimized key-value persisted store that is backed by a property list, and it is most commonly used for saving small pieces of data like user preferences. Despite its ease-of-use, there is one common anti-pattern I see developers use often.

Continue…

Xcode 15 introduces a new “bookmarks” feature, which lets you bookmark lines or entire files. It is a welcome change that has sherlocked my hack for using breakpoints as bookmarks.

Continue…

Beginning with the introduction of dark mode in iOS 13, colors in iOS are now (optionally) dynamic. You can provide light and dark variants for all colors in your app. However, I was surprised to find that SwiftUI — which also made its first appearance on the platform in iOS 13 — still does not provide any API for creating dynamic colors.

Continue…

I recently asked on Mastodon for tips on estimating your total number of RSS subscribers. It turns out it is rather easy to do. While I do have (privacy-aware) analytics for my site, this only tracks page views.

Continue…

When you display text in your app, you might come across situations where the text layout produces undesirable results under certain layout constraints. The text could wrap on smaller devices or be truncated in certain localizations. At this point, we are well-equipped with adaptive APIs to make our layouts work on all screen sizes — for example, we have Dynamic Type, Auto Layout, and UITraitCollection.

Continue…