CHAPTER 8

Some Pattern Principles

Although design patterns simply describe solutions to problems, they tend to emphasize solutions that promote reusability and flexibility. To achieve this, they manifest some key object-oriented design principles. We will encounter some of them in this chapter and in more detail throughout the rest of the book.

This chapter will cover

• Composition: How to use object aggregation to achieve greater flexibility than you could with inheritance alone
• Decoupling: How to reduce dependency between elements in a system
• The power of the interface: Patterns and polymorphism
• Pattern categories: The types of pattern that this book will cover