Part II: The Limitations of Traditional Object-Oriented Design

Part Overview

In this part, I solve a real-world problem using standard object-oriented methods. This was a problem I worked on when I was just beginning to learn design patterns.

Chapter	Discusses These Topics
3	A description of the CAD/CAM problem: extract information from a large computer-aided design/computer-aided manufacturing (CAD/CAM) database to feed a complex and expensive analysis program. Because the CAD/CAM system continues to evolve, the problem cries out for flexible code.
4	My first solution to the CAD/CAM problem, using standard object-oriented methods. At the time I actually worked on this problem, I hadn't yet learned the essence of the principles behind many design patterns. This resulted in an initial solution that over-relied on inheritance. It was easy to design and the initial solution worked, but I ended up with too many special cases. My solution had significant problems—difficult maintenance and inflexibility—just the things I hoped to avoid with object-oriented design. Later, in Part IV, I will revisit the problem in Chapter 12, “Solving the CAD/CAM Problem with Patterns.” I will solve the problem again using design patterns to orchestrate the application's architecture and its implementation details. By doing this, I create a solution that is much easier to maintain and is much more flexible.

This part is important to read because it illustrates a typical problem that results in traditional object-oriented design—taller-than-necessary inheritance hierarchies that have tight coupling and low cohesion.