[SOLVED] [Qwt and a DB] How to plot data coming from a DB with Qwt

valandil211

Hello Qt devs!

I have written this so far, but the code won't compile:

@
xAxisTime = new QSqlQuery;
xAxisTime->prepare("SELECT date(qa."QA_Timestamp") FROM "v_TestResults"");
xAxisTime->exec();
xAxisTime->next();

// Preperation of general query to fetch test results
yAxis = new QSqlQuery;
yAxis->prepare("SELECT \"OUT_Output\" FROM \"v_TestResults\" WHERE \"OUT_IndexResultat\" = :idtest, \"OUT_Minor\" = :row, \"OUT_Minor\" = :col");
yAxis->bindValue(":idtest", 20);
yAxis->bindValue(":row", 1);
yAxis->bindValue(":col", 1);
yAxis->exec&#40;&#41;;
yAxis->next(&#41;;

plotDsi0 = new QwtPlotCurve(trUtf8("DSI0"));
plotDsi0->setAxis(QwtPlot::xBottom, QwtPlot::yLeft);
plotDsi0->setData(xAxisTime->value(1).toDouble(), yAxis->value(1).toDouble(),
                  yAxis->size());

plotDsi0->attach(CKV2_qwtPlot);

@

The compiler complains: that

@
there is no matching function call to 'QwtPlotCurve::setData(double, double, int)'
@

However, there is a candidate that is:

@
QwtPlotcurve:: setData(const double*, const double*, int)
@

I guess I could use vectors, but I'm not familiar with them, yet. Is there another way to proceed?

Thanks for your tips!

soroush

you should pass pointers to your function.
@
double x = xAxisTime->value(1).toDouble();
double y = yAxis->value(1).toDouble();
plotDsi0->setData(&x, &y, yAxis->size());
@

EDIT:

Primitives have ctors, so this will work too:
@
plotDsi0->setData(new double(xAxisTime->value(1).toDouble()), new double(yAxis->value(1).toDouble()),
yAxis->size());
@

valandil211

Pointers to the QSqlQuery? But that won't return the actual record stored in the query. Plus, it won't return a double. I'm not sure I understand what you mean.

valandil211

Thanks @soroush. It worked perfectly.