[Qt-interest] [Properties] The NOTIFY signal, and the READ and WRITE functions

[Thiago Macieira]

Em Quinta-feira 28 Janeiro 2010, às 15:23:33, Louis Du Verdier escreveu:
> Hello,
> 
> In a project, I have to use properties with the NOTIFY signal. So I have
> declared the following property : Q_PROPERTY(bool myProperty READ getValue
> WRITE setValue NOTIFY valueChanged); In my opinion, the READ and WRITE
> functions, like the NOTIFY signal, should not be managed by me, but I
> don't manage them, my compilator say that my code have mistakes. It don't
> say anything if I write my WRITE function like it :
> void MyWidget::setValue(bool v)
> {
>         value = QVariant(v);
>         emit valueChanged(v);
> }
> But if we have to manage the acessor/... functions, what is the utility of
> properties ? So I think my code is wrong, and that I have forgoten
> something.

Declaring the Q_PROPERTY means moc will extract the information about your 
property and add to the meta object.

That means you can do run-time reflection into the objects and find out what 
they have available. Take a look at the QMetaObject and QMetaProperty classes.

This run-time reflection mechanism is used by a couple other Qt technologies. 
It's used by both QtScript and QtDBus to determine what from your object can 
be exported to the script/D-Bus environment.

It's also used by the upcoming QtDeclarative module to determine what is 
exported from your class into the QML world.

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
  Senior Product Manager - Nokia, Qt Development Frameworks
      PGP/GPG: 0x6EF45358; fingerprint:
      E067 918B B660 DBD1 105C  966C 33F5 F005 6EF4 5358
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