KeychainWrapper.swift

final class SharedTokenManager {
    
    private let tokenKey = "token"
    private let accessGroup: String
 
    init(accessGroup: String) {
        self.accessGroup = accessGroup
    }
    
    func getToken() -> String? {
        let queryLoad: [String: AnyObject] = [
          kSecClass as String: kSecClassGenericPassword,
          kSecAttrAccount as String: tokenKey as AnyObject,
          kSecReturnData as String: kCFBooleanTrue,
          kSecMatchLimit as String: kSecMatchLimitOne,
          kSecAttrAccessGroup as String: accessGroup as AnyObject
        ]

        var result: AnyObject?

        let resultCodeLoad = withUnsafeMutablePointer(to: &result) {
          SecItemCopyMatching(queryLoad as CFDictionary, UnsafeMutablePointer($0))
        }

        if resultCodeLoad == noErr {
          if let result = result as? Data,
            let keyValue = NSString(data: result,
                                    encoding: String.Encoding.utf8.rawValue) as? String {

            // Found successfully
            print(keyValue)
            return keyValue
          }
        } else {
          print("Error loading from Keychain: \(resultCodeLoad)")
        }
        return nil
    }
  
  func setToken(token: String) {
        guard let valueData = token.data(using: String.Encoding.utf8) else {
          print("Error saving text to Keychain")
          return
        }

        let queryAdd: [String: AnyObject] = [
          kSecClass as String: kSecClassGenericPassword,
          kSecAttrAccount as String: tokenKey as AnyObject,
          kSecValueData as String: valueData as AnyObject,
          kSecAttrAccessible as String: kSecAttrAccessibleWhenUnlocked,
          kSecAttrAccessGroup as String: accessGroup as AnyObject
        ]

        let resultCode = SecItemAdd(queryAdd as CFDictionary, nil)

        if resultCode != noErr {
          print("Error saving to Keychain: \(resultCode)")
        }
  }
}