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Design Patterns Explained

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CHAPTER 21<br />

<strong>Design</strong> <strong>Patterns</strong> Reviewed<br />

from the New Perspective of<br />

Object-Oriented <strong>Design</strong><br />

Overview<br />

At the end of any book, it is always nice to step back and see what we<br />

have gained. In this book, I have tried to give you a better and<br />

perhaps new understanding of object-oriented principles by teaching<br />

you design patterns and understanding how design patterns<br />

explain the object-oriented paradigm.<br />

In this chapter, I review the following:<br />

• The new perspective of object-oriented principles, based on an<br />

understanding of design patterns<br />

• How design patterns help us encapsulate implementations<br />

• Commonality/Variability analysis and design patterns and how<br />

they help to understand abstract classes<br />

• Decomposing a problem domain by the responsibilities involved<br />

• Specifying relationships between objects<br />

• <strong>Design</strong> patterns and contextual design<br />

Finally, I offer some field notes from my own practice.<br />

A Summary of Object-Oriented Principles<br />

In the course of the discussion on design patterns, I have stated a<br />

number of the principles of the object-oriented paradigm. These<br />

principles can be summarized as follows:<br />

In this chapter<br />

Objects from the new<br />

perspective<br />

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