C++/design patterns in the electromagnetic codes

It has been years since I slowly transform my program from C to C++ and I enjoy the object-oriented features provided in C++. They are powerful to generate reusable and extensible codes.

When talking with a computer science specialist, I find that it is the design pattern which are running behind the scene.

Design patterns are solutions using the OO features to the commonly encountered programming problems.

Has anyone ever considered the role of design patterns in programming computational electromagnetic codes? Has anyone used them in commercial/non-commercial codes?

Thank you.