“The so-called GoF book Design Patterns (GoF referring to the Gang of Four — Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides — who authored it) has been very influential in software development–and rightfully so. Every programmer has read it or at least claims to have done so. In this article, I will explore how Design Patterns are used in Qt programming. Qt article at O’Reilly site, by Matthias Kalle Dalheimer, author of Programming with Qt, 2nd Edition, a book to be released late February and it will cover the latest Qt 3.1 API.