turing complete with a stack of 0xdeadbeef
The main appeal of building apps in SwiftUI is being able to share UI code across platforms, in particular iOS and macOS. It is not perfect and you often have to do some #if os() checks, but when it works it is truly great. Before SwiftUI was around, you could already share a lot of (non-UI) code between iOS and macOS. Many of the system frameworks are available on both platforms, for example Foundation and Core Data. Occasionally there are API differences, but they rarely impose a significant burden.
If you are working on a multiplatform SwiftUI project, you will start accumulating #if os() checks and #if canImport() checks. Overtime, these start to accumulate and — in addition to being unsightly — they make your code much more difficult to read. When possible, I have started to encapsulate these preprocessor directives to improve code organization and readability.
As of iOS 14 and macOS 11, you can define the entry-point and app lifecycle of your app in SwiftUI with the App protocol instead of using the traditional UIApplicationDelegate protocol from UIKit. However, SwiftUI is still missing the majority of APIs from UIKit. For any serious app, you’ll need to provide an app delegate.
I’ve spent this past week diving into SwiftUI, seriously, for the first time. As you know, I’ve been keeping my eye on it since it was released, but I’ve avoided it due to a combination of hesitancy, apprehension, and just being too busy with other projects and work. However, while taking some time off from contracting work, I decided to dive in.
I’ve been following what’s going on with SwiftUI since it was released with iOS 13 at WWDC 2019 and have even taken extensive notes, but I have avoided using it. As I wrote before, I mainly wanted to avoid dealing with bugs and workarounds that might make me less productive compared to using UIKit, which I know quite well. I’m very interested in learning and using it, I’m just hesitant given some of Apple’s history, like early years of Swift. I have no doubt that SwiftUI will be the future of Apple platform development, the question is when that future will arrive. This year the framework is debuting its third major release in iOS 15. How far has SwiftUI come, and is it ready for building serious apps?
A few months ago, I shared my notes and resources for learning about compilers and LLVM. It turned out to be pretty popular and folks seemed to find it useful. So I decided to do it again, but this time for SwiftUI. However, unlike learning about compilers and LLVM, I am not declaring bankruptcy with learning SwiftUI. While I have still not written a single line of SwiftUI code, I know I eventually will.