[Qt-interest] Sending derived objects through queued connections

[Mihail Naydenov]

Singnal - slot calls are not that diff from normal func calls.

Most of the things you do with func calls should also work with signal/slots.
The catches are:
 - return must be void
 - You have to register the type you pass using qRegisterMetaType (if a custom one).
 - The params are pasted aways by copy. (They need to be stored because the queued connection call is dеffered )

So  these are the basics, you should try it yourself if your scenario works.
MihailNaydenov 




----- Original Message ----
> From: Akos Polster <akos at pipacs.com>
> To: qt-interest at trolltech.com
> Sent: Thu, June 3, 2010 12:22:03 AM
> Subject: [Qt-interest] Sending derived objects through queued connections
> 
> Hi,

is it possible to send derived objects via signals (over 
> queued
connections), and be able to restore them on the receiver side. 
> How
should my base and derived classes look like? Or any alternatives 
> you
can recommend.

Naive example:

class Base {};
class 
> Derived: public Base {};

class Emitter {
signals:
  void 
> bang(const Base &b);
};

class Receiver {
protected 
> slots:
  void onBang(const Base &b) {
    if 
> (magic_convert(b from Base to Derived)) {
      // Bingo! Got 
> a Derived object as signal parameter
    }
  
> }
};

main() {
  Emitter e;
  Base b;
  Derived 
> d;
  Receiver r;
  connect(&e, SIGNAL(bang(const Base 
> &)), &r, SLOT(onBang(const Base
&)), QueuedConnection);
  
> emit e.bang(d);
  // run event loop
}

Thanks

~ 
> Akos.
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