Qt: meaning of slot return value?

Question

According to the documentation the return value from a slot doesn't mean anything.
Yet in the generated moc code I see that if a slot returns a value this value is used for something. Any idea what does it do?

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Here's an example of what I'm talking about. this is taken from code generated by moc. 'message' is a slot that doesn't return anything and 'selectPart' is declared as returning int.

case 7: message((*reinterpret_cast< const QString(*)>(_a[1])),(*reinterpret_cast< int(*)>(_a[2]))); break;
case 8: { int _r = selectPart((*reinterpret_cast< AppObject*(*)>(_a[1])),(*reinterpret_cast< int(*)>(_a[2])));
    if (_a[0]) *reinterpret_cast< int*>(_a[0]) = _r; }  break;

Answer 1

The return value is only useful if you want to call the slot as a normal member function:

class MyClass : public QObject {
    Q_OBJECT
public:
    MyClass(QObject* parent);
    void Something();
public Q_SLOTS:
    int Other();
};

void MyClass::Something() { int res = this->Other(); ... } Edit: It seems that's not the only way the return value can be used, the QMetaObject::invokeMethod method can be used to call a slot and get a return value. Although it seems like it's a bit more complicated to do.