[Solved] SIGNAL and SLOTS

DarkRoast

Hi all

I am wondering about SIGNAL and SLOTS

I have the following code:

@ for(int i = 0; i < NUMBERS; i++)
{
NumbersLabel[i] = new QLabel(" N" + QString::number(i+1));

    NumbersSpinBox[i] = new QSpinBox;
    NumbersSpinBox[i]->setRange(MINNUMBER, MAXNUMBER);
    NumbersSpinBox[i]->setSpecialValueText(" ");

    connect(NumbersSpinBox[i], SIGNAL(editingFinished()), this, SLOT(NumberEditingFinished(i)));

    hLayout->addWidget(NumbersLabel[i]);
    hLayout->addWidget(NumbersSpinBox[i]);
}@

I know it doesn't work... But it illustrates what I want.

I want to connect editingFinished() from all my SpinBoxe's to the SLOT NumberEditingFinished(). I was hoping that I could send a argument to the SLOT function, i.e I want to know who is emitting the signal.

How can I do this ? do I have to make my own SIGNAL somehow ? Or is there another way to do this ?

Thanks in advance
DarkRoast

Daniel S.

Hi!

If you just want to know which QObject (or QSpinBox in your example) is emitting the signal, just try
"QObject::sender()":http://doc.qt.nokia.com/4.7/qobject.html#sender.

@void MyObject::NumberEditingFinished
{
QObject* emittingObject = sender();
if(emittingObject == 0)
{
//slot is NOT activated by a signal
}
else
{
//slot is activated by a signal emitted from emittingObject
}
}@

Zlatomir

I'm not sure i got your problem correctly, but signal mapper looks like what you are looking for.

In "this":http://doc.qt.nokia.com/4.7/signalsandslots.html page you have documentation for signals and slots, including default parameters and signal mapper.

giesbert

Hi DarkRoast,

There are some things to tell you:

a slot might never have more parameters than the signal cobnnected to it, less is ok, but not more.

in a connect you can't define a value for a parameter, as the parameter of a slot is filled by the signal parameters

As Zlatomir already said, "QSignalMapper":http://doc.qt.nokia.com/4.7/qsignalmapper.html might solve your problem (or QObject::sender() which gives you a pointer to the signal sender object).

Once again:

It is ok to have signalA(class1, class2) connected to

slotA(class1, class2)
slotB()
slotC()

but not to

slotA(class1, class2, class3)

DarkRoast

Thanks for all your replies!

I ended with using QSignalMapper, as seen in code beneath:

@ QSignalMapper *signalMapper = new QSignalMapper(this);
connect(signalMapper, SIGNAL(mapped(int)), this, SLOT(NumberEditingFinished(int)));

for(int i = 0; i < NUMBERS; i++)
{
    NumbersLabel[i] = new QLabel(" N" + QString::number(i+1));

    NumbersSpinBox[i] = new QSpinBox;
    NumbersSpinBox[i]->setRange(MINNUMBER, MAXNUMBER);
    NumbersSpinBox[i]->setSpecialValueText(" ");

    signalMapper->setMapping(NumbersSpinBox[i], i);
    connect(NumbersSpinBox[i], SIGNAL(editingFinished()), signalMapper, SLOT(map()));

    hLayout->addWidget(NumbersLabel[i]);
    hLayout->addWidget(NumbersSpinBox[i]);
}@

This way my NumberEditingFinished(int) function always knows who is emitting the signal.

Thanks