Error: Defining QML types from C++

[Ibrahim]

Hi;

// messagebox.h
#ifndef MESSAGEBOX_H
#define MESSAGEBOX_H

#include <QObject>
#include <QMessageBox>

class MessageBox : public QObject
{
  Q_OBJECT
  Q_PROPERTY(QString message READ message WRITE set_message)
public:
  explicit MessageBox(QObject *parent = 0);
  inline void set_message(QString& msg);

signals:

public slots:
};

#endif // MESSAGEBOX_H

// messagebox.cpp
#include "messagebox.h"

MessageBox::MessageBox(QObject *parent) : QObject(parent)
{
}

void MessageBox::set_message(QString& msg)
{
  QMessageBox::information(this, tr(""), tr(msg));
}

// main.cpp
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QtQuick>

#include "messagebox.h"

int main(int argc, char* argv[])
{
  QGuiApplication app(argc, argv);

  qmlRegisterType<MessageBox>("MessageBox", 1, 0, "MessageBox");

  QQmlApplicationEngine engine;
  engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

  return app.exec();
}

I am running this application but I get this error message:
project\path\messagebox.h:5: error: C1083: Cannot open include file: 'QMessageBox': No such file or directory
Then I am changing QMessageBox to QDebug:

// messagebox.h
#include <QDebug>

// messagebox.cpp
void MessageBox::set_message(QString& msg)
{
  qDebug() << tr(msg);
}

And I get this error message:
GCC (MingW):
project\path\main.cpp:11: error: no matching function for call to 'qmlRegisterType(const char [11], int, int, const char [11])'
qmlRegisterType<MessageBox>("MessageBox", 1, 0, "MessageBox");
^
MSVC:
project\path\main.cpp:11: error: C2974: 'qmlRegisterType' : invalid template argument for 'T', type expected
Thanks.

[jsulm]

Regarding "'QMessageBox': No such file or directory"
do you have
QT += widgets
in your pro file?

[Ibrahim]

@jsulm Yes, I do. I include Qt += widgets in .pro file.
.pro File:

TEMPLATE = app

QT += qml quick
QT += widgets
CONFIG += c++11

SOURCES += main.cpp \
    messagebox.cpp

RESOURCES += qml.qrc

# Additional import path used to resolve QML modules in Qt Creator's code model
QML_IMPORT_PATH =

# Default rules for deployment.
include(deployment.pri)

HEADERS += \
    messagebox.h

[Ibrahim]

The problem continues.