Not understanding QtScript

[zephod]

I'm trying to learn about QT script and I'm clearly not understanding something basic.
Consider the following code:

#include <iostream>
 
#include <QApplication>
#include <QtScript>
#include <QObject>
 
using namespace std;
 
class MyClass : public QObject
{
public:
        int x;
};
 
int main(int argc, char* argv[])
{
        QApplication app(argc, argv);
 
        MyClass mc; 
        mc.x = 0;
 
        QScriptEngine eng;
        QScriptValue scriptClass = eng.newQObject(&mc);
        QScriptValue global = eng.globalObject();
        global.setProperty("myClass", scriptClass);
 
        QScriptValue res = eng.evaluate("myClass.x == 0");
        if (res.isBoolean())
        {   
                cout << "res is 0 = " << res.toBoolean() << endl;
        }   
        else
        {   
                cout << "res is not boolean!!!" << endl;
        }   
        return 0;
}

#include <iostream>

#include <QApplication>
#include <QtScript>
#include <QObject>

using namespace std;

class MyClass : public QObject
{
public:
        int x;
};

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

        MyClass mc; 
        mc.x = 0;

        QScriptEngine eng;
        QScriptValue scriptClass = eng.newQObject(&mc);
        QScriptValue global = eng.globalObject();
        global.setProperty("myClass", scriptClass);

        QScriptValue res = eng.evaluate("myClass.x == 0");
        if (res.isBoolean())
        {   
                cout << "res is 0 = " << res.toBoolean() << endl;
        }   
        else
        {   
                cout << "res is not boolean!!!" << endl;
        }   
        return 0;
}

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This prints "res is 0 = 0" when run. It seems that the script engine does know about myClass but the value of myClass.x is not set.
Can someone enlighten me?

Thanks,
Steve

[wysota]

"x" needs to be a regular Qt property for this to work.

[zephod]

Thanks wysota!

Changed MyClass to

class MyClass : puble QObject
{
    Q_PROPERTY(int x);
};

class MyClass : puble QObject
{
    Q_PROPERTY(int x);
};

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and

mc.x = 0;

mc.x = 0;

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to

mc.setProperty("x", 0);

mc.setProperty("x", 0);

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and now its working.

[wysota]

That's not entirely correct. Should be:

class MyClass : public QObject
  Q_OBJECT
  Q_PROPERTY(int x READ x WRITE setX)
public:
  MyClass(QObject *parent = 0) : QObject(parent) { m_x = 0; }
  int x() const { return m_x; }
public slots:
  void setX(int _x) { m_x = _x; }
private:
  int m_x;
};
 
mc.setX(0);

class MyClass : public QObject
  Q_OBJECT
  Q_PROPERTY(int x READ x WRITE setX)
public:
  MyClass(QObject *parent = 0) : QObject(parent) { m_x = 0; }
  int x() const { return m_x; }
public slots:
  void setX(int _x) { m_x = _x; }
private:
  int m_x;
};

mc.setX(0);

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[zephod]

It seems that what I did caused some dynamic properties to be created so that my program gave the answers I expected without actually being correct.
See my other post on Q_PROPERTY and Q_OBJECT.

[wysota]

I know, thus if you use my code above, it will work as expected.