a.swift

public extension StorageAware {
  func object<T: Codable>(ofType type: T.Type, forKey key: String) throws -> T {
    return try entry(ofType: type, forKey: key).object
  }

  func existsObject<T: Codable>(ofType type: T.Type, forKey key: String) throws -> Bool {
    do {
      let _: T = try object(ofType: type, forKey: key)
      return true
    } catch {
      return false
    }
  }
}