keychain_query-return.swift

// Ejecutamos la búqueda
let status = SecItemCopyMatching(query as CFDictionary, &item)

// Comprobamos si no aparece el elemento...
if status == errSecItemNotFound
{
    return Result.failure(KeychainError.passwordNotFound)
}

// ...y en caso de encontrarlos lo procesamos
if status == errSecSuccess
{
    guard let existingItem = item as? [String : Any],
          let passwordData = existingItem[kSecValueData as String] as? Data,
          let password = String(data: passwordData, encoding: .utf8),
          let account = existingItem[kSecAttrAccount as String] as? String
    else
    {
        return Result.failure(KeychainError.malformedData)
    }

    let user = User(named: account, withPassword: password)

    return Result.success(user)
}
else
{
    return Result.failure(KeychainError.unknown(status: status))
}