[Qt-interest] Objective-C like message-passing

[Peter Kümmel]

Ross Bencina wrote:
> Hi Peter
> 
> I use QMetaObject::invokeMethod a little bit for this kind of thing.
> It's pretty easy to use once you realise that it doesn't use the same
> method signature syntax as connect():
> http://doc.trolltech.com/4.5/qmetaobject.html#invokeMethod
> 
> I'm not sure what advantages/disadvantages your idea has over this
> though...
> 

Hi Ross,

QMetaMeassage uses QMetaObject::invokeMethod with some more advanced C++ techniques to
drop the Q_ARG macros.

the code from the docs

QMetaObject::invokeMethod(pushButton, "animateClick", Qt::QueuedConnection); becomes

pushButton->take("animateClick", Qt::QueuedConnection)();

and

QString retVal;
QMetaObject::invokeMethod(obj, "compute", Qt::DirectConnection,
                           Q_RETURN_ARG(QString, retVal),
                           Q_ARG(QString, "sqrt"),
                           Q_ARG(int, 42),
                           Q_ARG(double, 9.7));

becomes

QString retVal = obj->take("compute").reply<QString>("sqrt", 42, 9.7);


I assume you see the advantage ;)
A disadvantaged is: each passed type must define QTypeInfo<T>::name().

Reading this I thought, why not adding takeQueued and takeDirekt?

Peter


> Ross.
>