Hello everyone

I created 30 QwtPlot projects.

//--mainwindow.h---
QwtPlot *qwtpt;
QPolygonF *polygon;
QwtPlotCurve *curve;
QwtPlotGrid *grid;
QwtSymbol *symbol;

//---mainwindow.cpp ----
int numplots = 30;
qwtpt = new QwtPlot[numplots];
polygon = new QPolygonF[numplots];
curve = new QwtPlotCurve[numplots];
grid = new QwtPlotGrid[numplots];
symbol = new QwtSymbol[numplots];

// do some setting
QString style = "color: white; ";
QPolygonF initialpoint;

initialpoint << QPointF(0.0f, 0.0f);

int k;
for(k = 0; k < numplots; ++k){
//plot
qwtpt[k].setParent(ui->scrollAreaWidgetContents_2);
qwtpt[k].setGeometry(1081, 20 + 181 * k, 760, 161);
qwtpt[k].setAxisTitle(QwtPlot::xBottom, "point");
qwtpt[k].setAxisTitle(QwtPlot::yLeft, "efficient %");
qwtpt[k].setAxisScale(QwtPlot::xBottom, 0.0, 132);
qwtpt[k].setAxisScale(QwtPlot::yLeft, 0.0, 100);
qwtpt[k].setStyleSheet(style);

//symbol
symbol[k].setPen(QPen(Qt::red, 2));
symbol[k].setStyle(QwtSymbol::Ellipse);
symbol[k].setBrush(QBrush(Qt::yellow));
symbol[k].setSize(QSize(8,8));

//curve
curve[k].setPen(Qt::blue, 4);
curve[k].setRenderHint(QwtPlotItem::RenderAntialiased, true);
curve[k].setSymbol(&symbol[k]);
curve[k].attach(&qwtpt[k]);
curve[k].setSamples(initialpoint);

//grid
grid[k].attach(&qwtpt[k]);
}
QwtPlot array crashed when I delete it


MainWindow::~MainWindow()
{

delete [] grid;
delete [] symbol;
delete [] polygon;

delete [] qwtpt; //on this line, program crash
delete [] curve;

}
when I do not delete the qwtplot array, the Qt debug show the program is crashed on MainWindow::~MainWindow()

Maybe I must to do something before delete qwtplot array;

Can anyone help me or give me some suggestion;

Thanks in advance.