User Defaults Wrapper Swift

UserDefaultsWrapper.swift

/// A wrapper around `NSUserDefaults` access for settings that are specific to the PlanGrid app.
/// `NSUserDefaults` should always be accessed through this type, this way we have a good overview
/// of all the settings the app supports and we can document them.
@objc final class PlanGridUserDefaults: NSObject {

    /// Keeps track of whether or not a user has already used the annotation filter feature.
    static var hasUsedAnnotationFilterFeature = UserDefaultsProperty<Bool>("HasUsedAnnotationFilterFeature")
}

/// A property that wraps around a value that is persisted to NSUserDefaults.
final class UserDefaultsProperty<T> {

    let identifier: String

    init(_ identifier: String) {
        self.identifier = identifier
    }

    // Would like to make the value property non-optional. But that depends on a fix/workaround
    // for https://bugs.swift.org/browse/SR-4479.
    var value: T? {
        set {
            UserDefaults.standard.set(newValue, forKey: self.identifier)
        }
        get {
            return UserDefaults.standard.object(forKey: self.identifier) as? T
        }
    }

}