congdong007

Penetration Test、Software Developer

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In Qt, how to transmit custom data using QAction::setData

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Recently, in a project, there was a need to transmit custom data using QAction::setData. I’ve searched online for a lot of information, but it’s all a bit vague, and none of them hit the mark. Some even provide solutions that completely contradict Qt’s principles. Below is an example code I wrote:

  1. Custom data:
    Here, taking a custom class as an example, the code is as follows:
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//.h

#ifndef QNEWITEM_H
#define QNEWITEM_H

#include <QObject>

class QNewItem : public QObject
{

public:
    QNewItem(QObject *parent = 0);
    ~QNewItem();

    bool setUserInfo(QString& strName,qint16& nAge);

private:
    QString m_strName;
    qint16 m_nAge;
};
#endif // QNEWITEM_H
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//.cpp

#include "qnewitem.h"


QNewItem::QNewItem(QObject *parent)
: QObject(parent)
{

}


QNewItem::~QNewItem()
{

}

bool QNewItem::setUserInfo( QString& strName,qint16& nAge )
{
    bool bRet = false;
    do
    {
        if( strName.isEmpty() || nAge >200 && nAge<0 ) break;

        m_strName = strName;
        m_nAge = nAge;
        bRet = true;
    } while (false);
    return bRet;
}
  1. At the beginning of the calling CPP file, you must declare it like this:
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#include "qnewitem.h"

Q_DECLARE_METATYPE(QNewItem*)

There’s not much else to say; when you look at the code, you’ll understand everything.

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#include "qnewitem.h"

Q_DECLARE_METATYPE(QNewItem*)

customDefineDemo::customDefineDemo(QWidget *parent, Qt::WFlags flags)
: QMainWindow(parent, flags)
{
    ui.setupUi(this);
    connect(ui.pushButton , SIGNAL(clicked()),this,SLOT(onBtnClick()));
}

customDefineDemo::~customDefineDemo()
{

}

void customDefineDemo::onBtnClick()
{
    QMenu* pMenu = new QMenu();
    QNewItem* pNewItem = new QNewItem();
    qint16 nAge = 34;
    QVariant qv;
    do
    {
        QAction* pPortraitView = new QAction(tr("New"), this);
        QAction* pAddGroup = new QAction(tr("Open"), this);
        QAction* pDeleteGroup = new QAction(tr("Save"), this);

        pNewItem->setUserInfo(tr("Eric"),nAge);

        pPortraitView->setData( QVariant::fromValue(pNewItem) ) ;

        connect(pPortraitView,SIGNAL(triggered()),this,SLOT(triggeredMenuSendMsgContact()));

        pMenu->addAction(pPortraitView);
        pMenu->addAction(pAddGroup);
        pMenu->addAction(pDeleteGroup);
        pMenu->exec(QCursor::pos());
    } while (false);

    if( pMenu != nullptr )
    {
        delete pMenu;
        pMenu = nullptr;
    }
}

void customDefineDemo::triggeredMenuSendMsgContact()
{
    QAction* pSendMsg= NULL;
    QNewItem* pObj = NULL;
    do
    {
        pSendMsg=qobject_cast<QAction*>(sender());

        pObj = pSendMsg->data().value<QNewItem*>();
    } while (false);

    if( pObj != nullptr )
    {
        delete pObj;
        pObj = nullptr;
    }
}