Hello
i have a problem.
What i try to do is to open a dialog when i click a button.
But i get a error when i compile can someone help me pls.

mainwindowimpl.cpp
#include "mainwindowimpl.h"
#include "dialogimpl.h"
//
MainWindowImpl::MainWindowImpl( QWidget * parent, Qt::WFlags f)
: QMainWindow(parent, f)
{
setupUi(this);
}
//

void MainWindowImpl:n_start_clicked()
{
DialogImpl * dia = new DialogImpl(this);
dia->show();
}

Error message!!
error.jpg

Thanks already!!