Other Advantages to Studying Design Patterns

My experience with development groups working with design patterns is that design patterns helped both individual learning and team development. This occurred because the more junior team members saw that the senior developers who knew design patterns had something of value and these junior members wanted it. This provided motivation for them to learn some of these powerful concepts.

Most design patterns also make software more modifiable. The reason for this is that they are time-tested solutions. Therefore, they have evolved into structures that can handle change more readily than what often first comes to mind as a solution.

Design patterns, when they are taught properly, can be used to greatly increase the understanding of basic object-oriented design principles. I have seen this countless times in the introductory object-oriented courses I teach. In those classes, I start with a brief introduction to the object-oriented paradigm. I then proceed to teach design patterns, using them to illustrate the basic object-oriented concepts (encapsulation, inheritance, and polymorphism). By the end of the three-day course, although we've been talking mostly about patterns, these concepts—which were just introduced to many of the participants—feel like they are old friends.

The Gang of Four suggests a few strategies for creating good object-oriented designs. In particular, they suggest the following:

• Design to interfaces.

• Favor composition over inheritance.

• Find what varies and encapsulate it.

These strategies were employed in most of the design patterns discussed in this book. Even if you do not learn a lot of design patterns, studying a few should enable you to learn why these strategies are useful. With that understanding comes the ability to apply them to your own design problems even if you do not use design patterns directly.

Another advantage is that design patterns allow you or your team to create designs for complex problems that do not require large inheritance hierarchies. Again, even if design patterns are not used directly, avoiding large inheritance hierarchies will result in improved designs.