Model with Properties form AppStorage

Toggle.swift

import Foundation
import SwiftUI
import Combine
import PlaygroundSupport

struct Model {
    @AppStorage(wrappedValue: true, "Test") var isEnabled
}

struct MyView: View {
    
    @State var model = Model()
    @AppStorage(wrappedValue: true, "Test") var valueFromPreferences
    
    var body: some View {
        Form {
            Toggle("State", isOn: model.$isEnabled)
            Toggle("Preferences", isOn: $valueFromPreferences)
        }
    }
}

PlaygroundPage.current.setLiveView(MyView())

Thanks a lot! This works, but I see a few issues:

• The model is now a class, and for reasons that are out of scope here, that's not a good option for me. I am looking for extending a struct with a property, without making additional changes to the model.
• Observing the UserDefaults with a catch-all-notification triggers too often. You debounce it, but it still triggers a lot on unrelated changes. It'd be better to observe the key instead of the whole defaults.
• ObservableObject already has a default objectWillChange publisher that does not need to be overridden.

I went for a different approach in the meantime:

• I am still using a property wrapper, but that wraps the original AppStorage.
• In the View, I have to add the AppStorage as a View property that can trigger the update. This way I get around having to turn the struct into an observableObject class.
• I am using the projectedValue for getting the AppStorage.

import Foundation
import SwiftUI
import Combine
import PlaygroundSupport

@propertyWrapper
struct WrappedAppStorage<T> {
    
    init(wrappedValue defaultValue: T,
         _ key: String,store: UserDefaults = UserDefaults.standard) where T == Bool {
        self.appStorage = AppStorage<T>(wrappedValue: defaultValue, key, store: store)
    }
    
    let appStorage: AppStorage<T>
    
    var wrappedValue: T {
        get { appStorage.wrappedValue }
        set { appStorage.wrappedValue = newValue }
    }
    
    var projectedValue: AppStorage<T> { appStorage }
    
}

struct Model {
    @WrappedAppStorage(wrappedValue: true, "Test") var isEnabled
}

struct MyView: View {
    
    init(_ model: Model) {
        self._model = .init(initialValue: model)
        _valueFromModel = model.$isEnabled
    }

    @State var model: Model
    
    @AppStorage var valueFromModel: Bool
    @AppStorage(wrappedValue: true, "Test") var valueFromPreferences
    
    var body: some View {
        Form {
            Toggle("State", isOn: $valueFromModel)
            Toggle("Preferences", isOn: $valueFromPreferences)
        }
        .animation(.default)
    }
}

PlaygroundPage.current.setLiveView(MyView(Model()))