Deep copy of QScriptValue as a global object

Question

I have a program using QtScript for some automation. I added a bunch of C ++ functions and classes to the global scope of the script engine so that scripts can access them, for example:

QScriptValue fun = engine->newFunction( systemFunc );
engine->globalObject().setProperty( "system", fun );

I would like to be able to run several scripts in a row, each of which has a new global state. Therefore, if one script sets a global variable, for example

myGlobalVar = "stuff";

I want this variable to be deleted before the next script run. My method for doing this is to make a deep copy of the global script engine object and then restore it when the script ends. But deep copies do not work, as my function systemsuddenly breaks with an error:

TypeError: Result of expression 'system' [[object Object]] is not a function.

Here is my deep copy function adapted from:
http://qt.gitorious.org/qt-labs/scxml/blobs/master/src/qscxml.cpp

QScriptValue copyObject( const QScriptValue& obj, QString level = "" )
{
    if( obj.isObject() || obj.isArray() ) {
        QScriptValue copy = obj.isArray() ? obj.engine()->newArray() : obj.engine()->newObject();
        copy.setData( obj.data() );
        QScriptValueIterator it(obj);
        while(it.hasNext()) {
            it.next();
            qDebug() << "copying" + level + "." + it.name();
            if( it.flags() & QScriptValue::SkipInEnumeration )
                 continue;
            copy.setProperty( it.name(), copyObject(it.value(), level + "." + it.name()) );
        }
        return copy;
    }

    return obj;
}

( SkipInEnumerationwas introduced to avoid an infinite loop)

EDIT: I think part of the problem is that in the debugger (QScriptEngineDebugger) the functions and constructors that I added should be displayed as a type Function, but after copying they are displayed as a type Object. I have not yet found a good way to create a new function that duplicates an existing one (QScriptEngine :: newFunction accepts the actual function pointer).

Answer 1

I have earned. Here's a solution in case it is useful to anyone else:

QScriptValue copyObject( const QScriptValue& obj)
{
    if( (obj.isObject() || obj.isArray()) && !obj.isFunction() ) {
        QScriptValue copy = obj.isArray() ? obj.engine()->newArray() : obj.engine()->newObject();
        copy.setData( obj.data() );
        QScriptValueIterator it(obj);
        while(it.hasNext()) {
            it.next();
            copy.setProperty( it.name(), copyObject(it.value()) );
        }
        return copy;
    }

    return obj;
}

!obj.isFunction(), , . , isObject() true, , . Qt, .

, SkipInEnumeration. -. SkipInEnumeration , eval .

Answer 2

, QtScript, QScriptValue QScriptEngine . , QScriptEngine. . , :

• - , .
• , , .
• QScriptValue QScriptEngine, , , . .

- , , :

class ScriptCopier
{
public:
    ScriptCopier(QScriptEngine& toEngine)
        : m_toEngine(toEngine) {}

    QScriptValue copy(const QScriptValue& obj);

    QScriptEngine& m_toEngine;
    QMap<quint64, QScriptValue> copiedObjs;
};


QScriptValue ScriptCopier::copy(const QScriptValue& obj)
{
    QScriptEngine& engine = m_toEngine;

    if (obj.isUndefined()) {
        return QScriptValue(QScriptValue::UndefinedValue);
    }
    if (obj.isNull()) {
        return QScriptValue(QScriptValue::NullValue);
    }

    // If we've already copied this object, don't copy it again.
    QScriptValue copy;
    if (obj.isObject())
    {
        if (copiedObjs.contains(obj.objectId()))
        {
            return copiedObjs.value(obj.objectId());
        }
        copiedObjs.insert(obj.objectId(), copy);
    }

    if (obj.isQObject())
    {
        copy = engine.newQObject(copy, obj.toQObject());
        copy.setPrototype(this->copy(obj.prototype()));
    }
    else if (obj.isQMetaObject())
    {
        copy = engine.newQMetaObject(obj.toQMetaObject());
    }
    else if (obj.isFunction())
    {
        // Calling .toString() on a pure JS function returns
        // the function source code.
        // On a native function however toString() returns
        // something like "function() { [native code] }".
        // That why we do a syntax check on the code.

        QString code = obj.toString();
        auto syntaxCheck = engine.checkSyntax(code);

        if (syntaxCheck.state() == syntaxCheck.Valid)
        {
            copy = engine.evaluate(QString() + "(" + code + ")");
        }
        else if (code.contains("[native code]"))
        {
            copy.setData(obj.data());
        }
        else
        {
            // Do error handling…
        }

    }
    else if (obj.isVariant())
    {
        QVariant var = obj.toVariant();
        copy = engine.newVariant(copy, obj.toVariant());
    }
    else if (obj.isObject() || obj.isArray())
    {
        if (obj.isObject()) {
            if (obj.scriptClass()) {
                copy = engine.newObject(obj.scriptClass(), this->copy(obj.data()));
            } else {
                copy = engine.newObject();
            }
        } else {
            copy = engine.newArray();
        }
        copy.setPrototype(this->copy(obj.prototype()));

        QScriptValueIterator it(obj);
        while ( it.hasNext())
        {
            it.next();

            const QString& name = it.name();
            const QScriptValue& property = it.value();

            copy.setProperty(name, this->copy(property));
        }
    }
    else
    {
        // Error handling…
    }

    return copy;
}

. Qt- QScriptValue::objectId().