can't show my QDialog

[wysota]

You need to provide getter methods in the dialog class to do that. Or you can make the ui for the dialog public, but this is really not advised.

[high_flyer]

but on compile has the error
mainwindow.cpp:2222: error: initializing temporary from result of 'IADFUQParameterDialog::IADFUQParameterDialog(QWid get*)'

When allocating on the heap (using new) you have to use pointer:

IADFUQParameterDialog *dialog = new IADFUQParameterDialog(this);

IADFUQParameterDialog *dialog = new IADFUQParameterDialog(this);

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And if you need to access this pointer in other places as well, you will want to make it a member variable.

sorry, tried to use dialog.exec() and it showed...

Well, the difference between show() and exec() is the modality mode.
But both should work.
Have a look at the faqs for "I have created a widget/dialog and it is not visible when I call show(). Why?"