Swift 4钥匙链secitemupdate错误状态代码-50

我正在尝试使用一些密钥链代码来安全持久地存储一些敏感数据。我有保存和读取数据的功能,这些功能可以正常工作,但我似乎无法使更新的功能正常工作。

let kSecClassValue = NSString(format: kSecClass)
let kSecAttrAccountValue = NSString(format: kSecAttrAccount)
let kSecValueDataValue = NSString(format: kSecValueData)
let kSecClassGenericPasswordValue = NSString(format: kSecClassGenericPassword)
let kSecAttrServiceValue = NSString(format: kSecAttrService)
let kSecMatchLimitValue = NSString(format: kSecMatchLimit)
let kSecReturnDataValue = NSString(format: kSecReturnData)
let kSecMatchLimitOneValue = NSString(format: kSecMatchLimitOne)


public class KeychainService: NSObject {
    class func updatePassword(service: String, account:String, data: String) {
        if let dataFromString: Data = data.data(using: String.Encoding.utf8, allowLossyConversion: false) {
            // Instantiate a new default keychain query
            let keychainQuery: NSMutableDictionary = NSMutableDictionary(objects: [kSecClassGenericPasswordValue, service, account, kCFBooleanTrue, kSecMatchLimitOneValue], forKeys: [kSecClassValue, kSecAttrServiceValue, kSecAttrAccountValue, kSecReturnDataValue, kSecMatchLimitValue])
            let status = SecItemUpdate(keychainQuery as CFDictionary, [kSecValueDataValue:dataFromString] as CFDictionary)
            if (status != errSecSuccess) {
                if let err = SecCopyErrorMessageString(status, nil) {
                    print("Read failed: \(err)")
                    print("status: \(status)")
                }
            }
        }
    }
...

我不断得到错误状态-50,表示传递给函数的一个或多个参数无效。我试着看完那些文件,但没能想出任何有效的办法。

提前谢谢!