Design Patterns Explained

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 informa-
tion 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 solu
tion worked, but I ended up with too many special cases.
• My solution had significant problems— difficult mainte
nance 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.
In this section
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