1

Is there a way to create a SwiftUI Binding from a computed property that provides a get {} and set {} shorthand?

Creating bindings for existing read-write properties seems unnessecarily complicated and verbose:

extension UserDefaults {
    var isTrackingEnabled: Bool {
        get { bool(forKey: "isTrackingEnabled") }
        set { set(newValue, forKey: "foo") }
    }
}

struct TrackingView: View {
    @Binding private var isTrackingEnabled: Bool

    init(defaults: UserDefaults) {
        self._isTrackingEnabled = Binding(
            get: { defaults.isTrackingEnabled },
            set: { newValue in defaults.isTrackingEnabled = newValue }
        )
    }

    ...
}

I am aware that this specific example is already solved in SwiftUI with the @AppStorage property wrapper, I am rather looking to emulate the same behaviour in general without having to create too much boilerplate.

I am looking to create the following syntax: UserDefaults.standard.$isTrackingEnabled where the property wrapper's projected value can be used as well as the wrapped value but wrapping the property directly is forbidden:

extension UserDefaults {
    @Binding var isTrackingEnabled: Bool { // ❌ Non-static property 'isTrackingEnabled' declared inside an extension cannot have a wrapper
        Binding(
            get: { bool(forKey: "isTrackingEnabled") },
            set: { newValue in set(newValue, forKey: "foo") }
        )
    }
}

Could one create a macro to convert between the two get-set representations?

2

You probably don’t want to do this, as changes won’t cause your Views to be updated.

3

@anton’s property wrapper could store an ObservableObject. The property wrapper’s initializer would register for updates from whatever UserDefaults-like storage it’s wrapping and send() the observable object’s objectWillChangePublisher before updating the cached value.

Only in an extension.