Using QProcess in QtScript

[chiiph]

Hello everyone,

I'm trying to use QProcess from QtScript.

I've tried a lot of things, but it seems the only way I can make it build is by using Q_SCRIPT_DECLARE_QMETAOBJECT(QProcess, QObject*), and then do:

QScriptValue proc = engine.scriptValueFromQMetaObject<QProcess>();
engine.globalObject().setProperty("Process", proc);

QScriptValue proc = engine.scriptValueFromQMetaObject<QProcess>();
engine.globalObject().setProperty("Process", proc);

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But then I do in the script:

var n = new Process();
n.start("someapp");

var n = new Process();
n.start("someapp");

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And it results in TypeError: Result of expression 'n.start' [undefined] is not a function.

What am I doing wrong?

Thanks in advance

[tbscope]

Easy, Process is a QObject

You need to tell the script engine that Process is actually a QProcess.

What you have is correct but not complete. Also use qScriptRegisterMetaType()

[chiiph]

Can you be more specific?
It seems I need to specify a toScriptValue and fromScriptValue functions, but I'm not really sure how to do it.

Thanks!

[tbscope]

Something in the lines of:

class MyObject : public QObject
 {
     Q_OBJECT
     ...
 };
 
 Q_DECLARE_METATYPE(MyObject*)
 
 QScriptValue myObjectToScriptValue(QScriptEngine *engine, MyObject* const &in)
 { return engine->newQObject(in); }
 
 void myObjectFromScriptValue(const QScriptValue &object, MyObject* &out)
 { out = qobject_cast<MyObject*>(object.toQObject()); }
 
 ...
 
 qScriptRegisterMetaType(&engine, myObjectToScriptValue, myObjectFromScriptValue);

class MyObject : public QObject
 {
     Q_OBJECT
     ...
 };

 Q_DECLARE_METATYPE(MyObject*)

 QScriptValue myObjectToScriptValue(QScriptEngine *engine, MyObject* const &in)
 { return engine->newQObject(in); }

 void myObjectFromScriptValue(const QScriptValue &object, MyObject* &out)
 { out = qobject_cast<MyObject*>(object.toQObject()); }

 ...

 qScriptRegisterMetaType(&engine, myObjectToScriptValue, myObjectFromScriptValue);

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Edit: changed the code as mentioned on the Qt documentation website

[chiiph]

I had to change a bit the functions since QProcess can't be copied.

But now I'm having this issue:

/usr/include/qt4/QtCore/qmetatype.h: In static member function ‘static int QMetaTypeId2<T>::qt_metatype_id() [with T = QProcess]’:
/usr/include/qt4/QtCore/qmetatype.h:230:   instantiated from ‘int qMetaTypeId(T*) [with T = QProcess]’
/usr/include/qt4/QtCore/qmetatype.h:243:   instantiated from ‘int qRegisterMetaType(T*) [with T = QProcess]’
/usr/include/qt4/QtScript/qscriptengine.h:402:   instantiated from ‘int qScriptRegisterMetaType(QScriptEngine*, QScriptValue (*)(QScriptEngine*, const T&), void (*)(const QScriptValue&, T&), const QScriptValue&, T*) [with T = QProcess]’
mainwindow.cpp:69:   instantiated from here
/usr/include/qt4/QtCore/qmetatype.h:169: error: ‘qt_metatype_id’ is not a member of ‘QMetaTypeId<QProcess>’

/usr/include/qt4/QtCore/qmetatype.h: In static member function ‘static int QMetaTypeId2<T>::qt_metatype_id() [with T = QProcess]’:
/usr/include/qt4/QtCore/qmetatype.h:230:   instantiated from ‘int qMetaTypeId(T*) [with T = QProcess]’
/usr/include/qt4/QtCore/qmetatype.h:243:   instantiated from ‘int qRegisterMetaType(T*) [with T = QProcess]’
/usr/include/qt4/QtScript/qscriptengine.h:402:   instantiated from ‘int qScriptRegisterMetaType(QScriptEngine*, QScriptValue (*)(QScriptEngine*, const T&), void (*)(const QScriptValue&, T&), const QScriptValue&, T*) [with T = QProcess]’
mainwindow.cpp:69:   instantiated from here
/usr/include/qt4/QtCore/qmetatype.h:169: error: ‘qt_metatype_id’ is not a member of ‘QMetaTypeId<QProcess>’

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Any ideas?

Thanks again

[tbscope]

Yes, do not forget Q_DECLARE_METATYPE

[chiiph]

Right... I thought that was implicit since it's already a QObject...

But now:

/usr/include/qt4/QtCore/qprocess.h: In function ‘void* qMetaTypeConstructHelper(const T*) [with T = QProcess]’:
/usr/include/qt4/QtCore/qmetatype.h:196:   instantiated from ‘int qRegisterMetaType(const char*, T*) [with T = QProcess]’
mainwindow.cpp:4:   instantiated from here
/usr/include/qt4/QtCore/qprocess.h:224: error: ‘QProcess::QProcess(const QProcess&)’ is private
/usr/include/qt4/QtCore/qmetatype.h:142: error: within this context

/usr/include/qt4/QtCore/qprocess.h: In function ‘void* qMetaTypeConstructHelper(const T*) [with T = QProcess]’:
/usr/include/qt4/QtCore/qmetatype.h:196:   instantiated from ‘int qRegisterMetaType(const char*, T*) [with T = QProcess]’
mainwindow.cpp:4:   instantiated from here
/usr/include/qt4/QtCore/qprocess.h:224: error: ‘QProcess::QProcess(const QProcess&)’ is private
/usr/include/qt4/QtCore/qmetatype.h:142: error: within this context

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this isn't as easy as it sounded... at least to me...

[tbscope]

:-)

This isn't easy :-)

Wrap your QProcess in a QSharedPointer.
This whole QScript mess is very complex. On one hand you have to have copy constructors, but on the other hand, they are not allowed.
You can solve this by using a QSharedPointer

[chiiph]

I'm going to come out as the stupidest guy in here but... how can I wrap it with an object that isn't a QObject?

[tbscope]

Note: I didn't compile this, so there might be a syntax error.

Example:

QScriptValue qScriptValueFromProcess(QScriptEngine *engine, const QSharedPointer<QProcess> &object)
{
    return engine->newQObject(object.data());
}
 
void qScriptValueToProcess(const QScriptValue & value, QSharedPointer<QProcess> & object)
{
}
 
Q_SCRIPT_DECLARE_QMETAOBJECT(QProcess, QObject*)
Q_DECLARE_METATYPE(QSharedPointer<QProcess>)
 
QScriptValue processValue = m_engine->scriptValueFromQMetaObject<QProcess>();
m_engine->globalObject().setProperty("Process", processValue);
 
qScriptRegisterMetaType(m_engine, qScriptValueFromProcess, qScriptValueToProcess);

QScriptValue qScriptValueFromProcess(QScriptEngine *engine, const QSharedPointer<QProcess> &object)
{
    return engine->newQObject(object.data());
}

void qScriptValueToProcess(const QScriptValue & value, QSharedPointer<QProcess> & object)
{
}

Q_SCRIPT_DECLARE_QMETAOBJECT(QProcess, QObject*)
Q_DECLARE_METATYPE(QSharedPointer<QProcess>)

QScriptValue processValue = m_engine->scriptValueFromQMetaObject<QProcess>();
m_engine->globalObject().setProperty("Process", processValue);

qScriptRegisterMetaType(m_engine, qScriptValueFromProcess, qScriptValueToProcess);

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m_engine is a member variable containing a pointer to a script engine.

[chiiph]

Great, so now it built, but it's the same problem as before, I can declare a variable, assign new Process(), but when I call variable.start("ls") it's the same error...

Any ideas?