qdbus和自定义类型的编组

Question

我想通过Qt DBUS API发送一个自定义的c++类。我已经使用protoc编译器从.proto文件创建了这个类，并将它们添加到我的QtCreator项目中。现在，我要验证是否可以通过dbus API将定制类作为QVariant发送。我有一个接收器和发送器程序，可以发送一个简单的测试字符串，所以Dbus工作。在将protocol buffer类添加为元类型后，我在发送它时遇到了问题。

我的测试.proto文件只包含int：

message MyData {
  required int32 name = 1;
  required int32 id = 2;
  optional int32 email = 3;
}

在我添加的protocol buffer类头文件中：

#include <QMetaType>
#include <QDBusMetaType>
...
friend QDBusArgument &operator<<(QDBusArgument &argument, const MyData &dataToWrite);
friend const QDBusArgument &operator>>(const QDBusArgument &argument, MyData &dataToWrite);
...
Q_DECLARE_METATYPE(MyData )

和我添加的协议缓冲区类实现文件：

#include <QDebug>
...
#include <QMetaType>
#include <QDBusMetaType>

// Marshall the MyData data into a D-Bus argument
QDBusArgument &operator<<(QDBusArgument &argument, const MyData &dataToWrite)
{

    qDebug() << "OPERATOR<<";

    argument.beginStructure();

    // Break out the various properties of dataToWrite protocol buffer
    int name = dataToWrite.name();
    int id = dataToWrite.id();
    int email = dataToWrite.email();
    qDebug() << name;
    qDebug() << id;
    qDebug() << email;

    argument << name;
    argument << id;
    argument << email;
    argument.endStructure();
    return argument;

}

// Retrieve the MyData data from the D-Bus argument
const QDBusArgument &operator>>(const QDBusArgument &argument, MyData &dataToWrite)
{

    qDebug() << "OPERATOR>>";

    argument.beginStructure();

    // Break out the various properties of dataToWrite protocol buffer
    int name = dataToWrite.name();
    int id = dataToWrite.id();
    int email = dataToWrite.email();
    qDebug() << name;
    qDebug() << id;
    qDebug() << email;

    argument >> name;
    argument >> id;
    argument >> email;
    argument.endStructure();
    return argument;

}

Main看起来就像这样：

QCoreApplication a(argc, argv);

    dbussender* client = new dbussender("com.one.two.three.nvram", "/dbusReadWriteNvRam", QDBusConnection::sessionBus(), 0);

    // Create a protocol buffer class and provide its properties with values
    MyData dataToWrite;
    dataToWrite.set_name(2);
    dataToWrite.set_id(3);
    dataToWrite.set_email(4);

    QString command3 = "Contacting Protobuf Receiver and calling WRITENVRAM...";
    QString response3 = client->writeNVRam(dataToWrite);

    std::cout << "Command:   " << command3.toStdString() << std::endl;
    std::cout << "Response:   " << response3.toStdString() << std::endl;

我的dbussender类像这样调用远程函数：

inline QDBusPendingReply<QString> writeNVRam(MyData dataToWrite)
    {

        qDebug() << "Sending " << dataToWrite.name();
        qDebug() << "Sending " << dataToWrite.id();
        qDebug() << "Sending " << dataToWrite.email();

        QList<QVariant> argumentList;
        argumentList << QVariant::fromValue<MyData>(dataToWrite);
        return asyncCallWithArgumentList(QLatin1String("writeNVRam"), argumentList);
    }

最终在我的接收器程序中，这个函数被调用，但总是返回0：

// Write NVRAM
QString dbusReadWriteNvRam::writeNVRam(MyData dataToWrite) {

    qDebug() << "WRITE NVRAM COMMAND CALLED";

    qDebug() << "Unpacking: " << dataToWrite.name();
    qDebug() << "Unpacking: " << dataToWrite.id();
    qDebug() << "Unpacking: " << dataToWrite.email();

    return "HELLO CLASS";

}

以下是Sender程序的输出：

Sending  2 
Sending  3 
Sending  4 
OPERATOR<< 
0 
0 
0 
OPERATOR<< 
2 
3 
4 
Command:   Contacting Protobuf Receiver and calling WRITENVRAM...
Response:   HELLO CLASS

下面是接收器程序的输出：

OPERATOR<< 
0 
0 
0 
OPERATOR>> 
0 
0 
0 
WRITE NVRAM COMMAND CALLED 
Unpacking:  0 
Unpacking:  0 
Unpacking:  0

为什么编组函数似乎被调用了两次？为什么第二个调用似乎包含了我的protocol buffer的3个属性的有效值2,3,4，但是第一个调用都是0？接收器似乎只看到全0，并且从不接收具有有效值的协议缓冲区对象。

我的编组代码有问题吗？还能发生什么呢？

Answer 1

要实现此操作，请像这样实现运算符：

// PROTOBUF-MODIFICATION-DBUS
// Marshall the companyData data into a D-Bus argument
QDBusArgument &operator<<(QDBusArgument &argument, const companyData &dataToWrite)
{

    argument.beginStructure();

    // Break out the various properties of dataToWrite protocol buffer
    int name = dataToWrite.name();
    int id = dataToWrite.id();
    int email = dataToWrite.email();
    argument << name;
    argument << id;
    argument << email;
    argument.endStructure();
    return argument;

}

// PROTOBUF-MODIFICATION-DBUS
// Retrieve the companyData data from the D-Bus argument
const QDBusArgument &operator>>(const QDBusArgument &argument, companyData &dataToWrite)
{

    int name, id, email;

    argument.beginStructure();
    argument >> name;
    argument >> id;
    argument >> email;
    argument.endStructure();
    dataToWrite.set_name(name);
    dataToWrite.set_id(id);
    dataToWrite.set_email(email);
    return argument;

}