[Qt-interest] problem with signal/slot

[Mahendra G.R]

Hi,

yes i do put it in a seperate cpp file, just to make it look shorter in the
mail i did that :), but still no use, it says method is not found. any other
reasons?, thanks for your reply.

On Wed, Dec 8, 2010 at 6:08 PM, Xiaolei Shang <xiaolei.shang at cobham.com>wrote:

>  Hi:
>
> Hi guys,
>
> i have a small problem with signal/slot, though i have defined my slot
> method, i get runtime message saying   Object::connect: No such slot
> CustomScene::updateAlphaValue()  , i have defined the method
> updateAlphaValue() in the customScene class
>
> this is my code :
>
> class CustomScene : public QGraphicsScene
> {
>
>     Q_OBJECT
>     public:
>         CustomScene()
>         {
>               alphaSlider = new QSlider(Qt::Horizontal);
>             alphaSlider->setTickInterval(1);
>             alphaSlider->setRange(0,255);
>             alphaSlider->setMinimumSize(105,20);
>             alphaSlider->move(6,222);
>             alphaSlider->setToolTip("Opacity");
>             connect( alphaSlider, SIGNAL(valueChanged(int)),
> SLOT(updateAlphaValue()) );
>          //some other stuff
>      }
>
> public slots :
>             void updateAlphaValue();
>
> };
> --
> http://www.mahendragr.com
>
>  If you move the declaration of updateAlphaValue() to the front of the
> definition of the constructor, the compiler should be able to see the
> function. Like this:
>
> class CustomScene : public QGraphicsScene
> {
>
>     Q_OBJECT
>
>    public slots :
>             void updateAlphaValue();
>
>     public:
>         CustomScene()
>         {
>               alphaSlider = new QSlider(Qt::Horizontal);
>             alphaSlider->setTickInterval(1);
>             alphaSlider->setRange(0,255);
>             alphaSlider->setMinimumSize(105,20);
>             alphaSlider->move(6,222);
>             alphaSlider->setToolTip("Opacity");
>             connect( alphaSlider, SIGNAL(valueChanged(int)),
> SLOT(updateAlphaValue()) );
>          //some other stuff
>      }
> ...
> };
>
> As you define your constructor in your declaration scope. You have to
> declare a function before you call it. Otherwise, the compiler won't see it.
> However, in this case, this is not a good way for defining the class as it
> contains many line codes. Implicitly, it's a online function. I would
> recommand to put the definition of the constructor in a .cpp file.
>
> Cheers
>
> Xiaolei
>
>
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>


-- 
http://www.mahendragr.com
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