Merge pull request steipete#9 from jasperblues/master

Add a more compelling (theoretical) justification for using Aspects

README.md

@@ -39,6 +39,24 @@ Aspects collects all arguments in the `arguments` array. Primitive values will b
 
 When to use Aspects
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+Aspect-oritented programming (AOP) is used to encapsulate "cross-cutting" concerns. These are the kind of requirements that *cut-accross* many modules in your system, and so cannot be encapsulated using normal Object Oriented programming. Some examples of these kinds of requirements: 
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+* *Whenever* a user invokes a method on the service client, security should be checked. 
+* *Whenever* a useer interacts with the store, a genius suggestion should be presented, based on their interaction. 
+* *All* calls should be logged. 
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+If we implemented the above requirements using regular OO there'd be some drawbacks: 
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+
+Good OO says a class should have a single responsibility, however adding on extra *cross-cutting* requirements means a class that a class is taking on other responsibilites. For example you might have a **StoreClient** that supposed to be all about making purchases from an online store. Add in some cross-cutting requirements and it might also have to take on the roles of logging, security and recommendations.   
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+* Our StoreClient is now harder to maintain
+* These cross-cutting requirements are duplicated and spreading throughout our app. 
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+AOP lets us modularize these cross-cutting requirements again. As shown in the examples above cross-cutting requirements can be eithe technical or business focused in nature.  
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+## Here are some concrete examples: 
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 Aspects can be used to **dynamically add logging** for debug builds only: