A Complete Guide To GOF Design Patterns (With Examples Of Observer, Decorator and Strategy Patterns)

Design patterns provide you a flexible way to solve common design problems. This article gives you a simple and effective introduction regarding learning and applying design patterns. In this article series, we will design a foot ball engine, analyze the design problems in that, and will apply patters to solve our design problems. In this way, you will learn how to actually use design patterns. The whole article and source code is included in the attached zip file.
<P><font size="4">T</font>his article is expected to</P>
<ul>
 <li>Introduce patterns to you in a simple, human readable (?) way</li>
 <li>Train you how to really 'Apply' patterns (you can learn patterns easily, 
 but to apply them to solve a problem, you need real design skills)</li>
 <li>Provide you a fair idea regarding the contexts for applying the following patterns - Builder, Observer, 
 Strategy and Decorator (well, they are few popular design patterns)</li>
 <li>Demonstrate you how to apply the Observer, Decorator and Strategy patterns, to solve the design 
 problems</li>
</ul>
<P>In this entire article, you will go through the following steps</P>
<ol>
 <li>You will model a very simple football game engine</li>
 <li>You will identify the design problems in your football game engine</li>
 <li>You will decide which patterns to use for solving your design problems</li>
 <li>You will then actually use the observer pattern, to solve one of your 
 design problem.</li>
</ol>
Download the article and related source code, and extract the zip file. You will see two parts of the article.