/UserPreferences

Observable preferences for SwiftUI with discriminating view updates

Primary LanguageSwiftMIT LicenseMIT

UserPreferences

UserPreferences is an alternative to SwiftUI's @AppStorage

Author

Axel Ancona Esselmann, axel@anconaesselmann.com

License

UserPreferences is available under the MIT license. See the LICENSE file for more info.

Motivation

SwiftUI's @AppStorage property wrapper is a convenient way to utilize UserDefaults. Sadly all Views that utilize @AppStorage will receive a refresh whenever any @AppStorage property is updated. UserPreferences is a small library that allows quick access to UserPreferences with granular View updates.

Example 1:

We define a preference-key-enum:

enum ExampleKey: String, UserPreferenceKey {
    case aIsOn, bIsOn
}

We inject our user preference store implementation into the view environment:

@main
struct OurApp: App {

    @StateObject
    var preferences = UserPreferences<ExampleKey>()

    var body: some Scene {
        WindowGroup {
            ContentView()
                .environmentObject(preferences)
        }
    }
}

by default UserDefaults is used to store preferences. Custom stores can be injected into the UserPreferences initializer.

We can now read preferences:

struct SomeView: View {

    @UserPreference(ExampleKey.aIsOn)
    var aIsOn: Bool = false

    var body: some View {
        Text(aIsOn ? "On" : "Off")
    }
}

and write preferences:

struct AnotherView: View {

    @UserPreference(ExampleKey.aIsOn)
    var aIsOn: Bool = false

    var body: some View {
        Toggle(
            "Set aIsOn",
            isOn: $aIsOn
        )
    }
}

Only views that toggle or read from aIsOn will update if aIsOn changes.

Example 2 and Example 3 show how we can use Sets and Arrays to group like preferences.

Example 4 shows how to use PublishedUserPreference to work with preferences inside a ViewModel