ICSNetwork Challenge Question

Q. If you look at the Qt source, the class QWidget has only one private non-static data member. This is surprising for a class that holds so much information. There is, in fact, a technical reason for this. What is it?

A. All data members of QWidget are in a separate class, accessible only through a private member of QWidget: the d-pointer. This technique, known under various names (d-pointer, Pimpl, handle/body or Cheshire Cat) is used because adding data members directly to the QWidget class between versions of the Qt library would break binary compatibility. For more information, see http://techbase.kde.org/Policies/Binary_Compatibility_Issues_With_C++

And the winner is: Ron Natalie, Herndon, VA

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An Introduction to Design Patterns in C++ with Qt 4 by Alan Ezust and Paul Ezust

C++ GUI Programming with Qt 4, Second Edition by Jasmin Blanchette and Mark Summerfield

Rapid GUI Programming with Python and Qt by Mark Summerfield

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