UserPreferences: A wrapper for UserDefaults

UserPreferences.swift

/// A class that provides a centralized way to access and modify stored preferences.
final class UserPreferences {
    static let shared = UserPreferences()
    private let userDefaults: UserDefaults

    /// Initializes the UserPreferences object with a UserDefaults instance.
    init(userDefaults: UserDefaults = .standard) {
        self.userDefaults = userDefaults
    }

    /// Subscript that provides a convenient way to access stored values.
    subscript<T>(key: PersistenceKey) -> T? {
        get { return userDefaults[key.rawValue] }
        set(newValue) {
            userDefaults[key.rawValue] = newValue
        }
    }

    /// Removes the stored value for the given key.
    func remove(key: PersistenceKey) {
        userDefaults.removeObject(forKey: key.rawValue)
        userDefaults.synchronize()
    }
}

/// Extension on UserDefaults that adds a subscript for convenient access to stored values.
extension UserDefaults {
    subscript<T>(key: String) -> T? {
        get { return object(forKey: key) as? T }
        set(newValue) {
            set(newValue, forKey: key)
            synchronize()
        }
    }
}

/// Enumeration of all the keys that are persisted in the UserDefaults.
enum PersistenceKey: String, CaseIterable {
    case onBoardingSeen
    case defaultCoin
}