Terminology: aspect
I continue to try and cut through some of the confusion around AOP by providing simple definitions and examples of often obtuse terminology (see also: other terminology posts).
"Aspect" seems like the core term in "aspect oriented programming" doesn't it? An aspect is simply a way to indicate to an AOP tool: what and where. The "what" is the advice, and the "where" are join points.
Let's review the terms covered so far by looking at a very trivial example of AOP:
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| public class MyClass | |
| { | |
| [MyAspect] | |
| public void MyMethod() | |
| { | |
| Console.WriteLine("inside of my method"); | |
| } | |
| } | |
| [Serializable] | |
| public class MyAspectAttribute : OnMethodBoundaryAspect | |
| { | |
| public override void OnEntry(MethodExecutionArgs args) | |
| { | |
| Logger.Write("some logging message"); | |
| } | |
| } |
In that example:
- The join point is "OnEntry", i.e. before a method is executed
- The advice is the body of the OnEntry method (Logger.Write(...))
- The aspect is the MyAspectAttribute class itself
- The pointcut is a combination of the applied [MyAspect] attribute along with the join point
- i.e. the complete pointcut is "before the MyMethod method of MyClass is executed"
- in this illustration, it's a very specific pointcut, but useful real-world pointcuts would be broader
- The cross-cutting concern is logging (haven't gotten to that term yet; what's the rush, it's only the name of the site!)
- The weaving is performed by the PostSharp post-compiler (also haven't gotten to that term yet)
Looks like two more terminology posts to go. If there's a term that I'm missing or glossing over, let me know, and I'll write a post on it.
