The sad state of @AppStorage and the Observable framework

You thought you could use @AppStorage and the new @Observable? Think again!

As weird as it seems, the @AppStorage new macro does not support the property wrapper. If, like me you had ObservableObject with @AppStorage properties in them, which were working precisely as @Published properties, it simply won’t compile once you migrate your object to @Observable.

But we have a solution, thanks to David Steppenbeck. He made a swift macro that allows a property to be backed by UserDefault and observed.

Update: David Steppenbeck also made a post on Medium about it!

Accessing UserDefaults within @Observable classes in iOS 17

You can add it as a Swift Package to your project.

GitHub - davidsteppenbeck/ObservableUserDefault: A Swift macro that adds accessor blocks to…

And you use it like so

import ObservableUserDefault

@Observable
final class StorageModel {
    @ObservableUserDefault(.init(key: "NAME_STORAGE_KEY", defaultValue: "John Appleseed", store: .standard))
    @ObservationIgnored
    var name: String
}

Unfortunately, in the case of Ice Cubes, I’ve made a lot of AppStorage use. I’ve made an extension to store Codable, and I keep a lot of enums also. I need to get familiar with Swift macros to add support to what I need in David’s macro.

So my UserPreferences and Theme environment object will stay ObservableObect for now. It’s the only two remaining objects I need to migrate to the new observation framework.

I am confident that Apple will provide proper AppStorage support in an upcoming minor release of the iOS SDK. It’s a bit crazy, honestly, that it was not included in the 17.0 release.