UserDefaults template with embedded auto-completion

Settings.swift

let defaults = UserDefaults.standard

// MARK: Keys
enum Keys: String, CaseIterable {
  case firstName
  case websiteUrl
  case hasLaunchedAppBefore
  
  /// The default value for a given UserDefaults key
  var defaultValue: Any {
    switch self {
    case .firstName: return "John"
    case .websiteUrl: return URL(string: "https://apple.com")
    case .hasLaunchedAppBefore: return false
    }
  }
}

// MARK: Settings
struct Settings {
  static let firstName: String = getValue(.firstName) as! String
  static let websiteUrl: URL = getValue(.websiteUrl) as! URL
  static var hasLaunchedAppBefore: Bool = getValue(.hasLaunchedAppBefore) as! Bool
  
  /// Returns the value for a given UserDefaults key
  static func getValue(_ forKey: Keys) -> Any {
    return defaults.value(forKey: forKey.rawValue) as Any
  }
  /// Saves a value to a given UserDefaults key
  static func saveValue(_ value: Any, forKey: Keys) {
    defaults.set(value, forKey: forKey.rawValue)
  }
  /// Returns the default value for any given UserDefaults key
  static func getDefaultValue(_ forKey: Keys) -> Any {
    return forKey.defaultValue
  }
  /// Reverts to the default value of the given UserDefaults key
  static func setDefaultValue(_ forKey: Keys) {
    defaults.set(forKey.defaultValue, forKey: forKey.rawValue)
  }
  /// Restore all values to their default state
  static func restoreAllDefaults() {
    for key in Keys.allCases {
      setDefaultValue(key)
    }
  }
  
}

// Iterate through all cases of Keys
extension Keys {
  static var allCases: [Self] {
    return Mirror(reflecting: self).children.compactMap { $0.value as? Self }
  }
}

Explicitly using String-based values for Settings

let defaults = UserDefaults.standard

// MARK: Keys
enum Keys: String {
  case myFirstKey
  
  /// The default value for a given UserDefaults key
  var defaultValue: String {
    switch self {
    case .myFirstKey: return "[default value for myFirstKey]"
    }
  }
}

// MARK: Settings
struct Settings {
  
  static let myFirstSetting = getValue(.myFirstValue)
  
  /// Returns the value for a given UserDefaults key
  static func getValue(_ forKey: Keys) -> String {
    return defaults.value(forKey: forKey.rawValue)
  }
  /// Saves a value to a given UserDefaults key
  static func saveValue(_ value: String, forKey: Keys) {
    defaults.set(value, forKey: forKey.rawValue)
  }
  /// Returns the default value for any given UserDefaults key
  static func getDefaultValue(_ forKey: Keys) -> String {
    return forKey.defaultValue
  }
  /// Reverts to the default value of the given UserDefaults key
  static func setDefaultValue(_ forKey: Keys) {
    defaults.set(forKey.defaultValue, forKey: forKey.rawValue)
  }
  
}


// MARK: Iterating Keys
extension Keys {
  static var allCases: [Self] {
    return Mirror(reflecting: self).children.compactMap { $0.value as? Self }
  }
}

// Usage Example: Restore all defaults
extension Settings {
  /// Restore all settings to their default value
  static func restoreAllDefaults() {
    for key in Keys.allCases {
      if key.rawValue != key.defaultValue {
        setDefaultValue(key)
      }
    }
  }
}