Design Patterns Explained

PART V
Handling Variations with
Design Patterns
Part Overview
In this part, I work through another case study. In this case study, I In this part
will consider the requirements for the problem one at a time, rather
than specifying every requirement up front. I will describe a system
that is currently working when a new requirement comes in that
forces me to find the best way to modify the code. I will use this
process to present a few new design patterns— one for each new
requirement.
Chapter Discusses These Topics
14 The Strategy pattern: How to handle varying algorithms and
business rules.
15 The Decorator pattern: How to dynamically add behavior
before or after an object's current behavior.
16 The Singleton pattern and the Double-Checked Locking
pattern: How to ensure not more than one instance of a class
is ever instantiated, even in a multithreaded environment.
17 The Observer pattern: How to let one part of a system know
when an event takes place in another.
18 The Template Method pattern: What to do when you have
different cases that use essentially the same procedure, but
their steps must be implemented in slightly different ways.
19 The Factory Method pattern: How to defer instantiation of
particular objects to derived classes.
20 The Analysis Matrix: How to track multiple variations that are
present in your problem domain and map them into patterns.
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