Textbooks and courses explain a design pattern by highlighting a situation, then providing a convenient solution: the pattern. There is nothing wrong with this when documenting a design pattern. The problem comes when the same sequence of steps is applied to recognize the design pattern directly from the requirements. The request is then captured in terms of a well-known design pattern. The design becomes rigid and unable to answer to changes in requirements. In this course on design patterns, students are actively pursued to not apply design patterns up-front. Design patterns come the other way around. Once a tailored solution is designed, parts of the design start exhibiting behavior which is a known hallmark of a certain design pattern. Only then do we change the design to accommodate the design pattern, and only because we have discovered the pattern in actual design. The key point is that a design pattern comes last to the design. Always with a relief; sometimes with a huge surprise in the form of a breakthrough.
Author Name: Zoran Horvat
Author Description:
Zoran Horvat is Principal consultant at Coding Helmet Consultancy, speaker and author of 100+ articles, and independent trainer on .NET technology stack. He can often be found speaking at conferences and user groups, promoting object-oriented development style and clean coding practices and techniques that improve longevity of complex business applications.