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POIs the Visitor pattern the best way to refactor domain enums to classes?
 

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  1. POIs the Visitor pattern the best way to refactor domain enums to classes?
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    <p>If we want to refactor an enum (contained in the domain layer) to a polymorphic class, using "simple" abstract methods could be a bad idea, if all the switch and if statements we want to refactor are inside the other layers (like the business or the presentation layer), because we could end up to reference these layers inside the domain layer:</p> <pre><code>public abstract class MyRefactoredEnum { public abstract void DoSomething(IBusinnessObject aBizObject); //dependency to the biz. layer public abstract MvcHtmlString GetImgTag(); //dependency to presentation layer } </code></pre> <p>(in the example above, we can have a "cross reference" problem too)</p> <p>I've found that the visitor pattern ( <a href="http://en.wikipedia.org/wiki/Visitor_pattern" rel="nofollow noreferrer">http://en.wikipedia.org/wiki/Visitor_pattern</a> ) it's a valid solution to this problem: in the domain layer we define only the MyRefactoredEnum.IVisitor interface, and all the other layers can implement their own visitors.</p> <p>The only problem: when we modify the MyRefactoredEnum.IVisitor interface (for example, because we've added another MyRefactoredEnum's subclass) we have to modify and recompile all projects and solutions that reference the domain model. We can solve the problem using reflection ( <a href="http://surguy.net/articles/visitor-with-reflection.xml" rel="nofollow noreferrer">http://surguy.net/articles/visitor-with-reflection.xml</a> ), but it can be slow...</p> <p>Is there a better pattern to refactor an enum? </p> <p>PS: sorry for my awful English :)</p>
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    1. USAdrian Grigore
    1. USNotoriousxl
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    1. COEnum is a c# keyword and simply a type that only allows n values (something like enum myEnum{value1,value2,...}; I can't really see any I think what you actually mean by refactoring that to a visitor pattern. Do you perhaps mean an enumerator?
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      1. USAdrian Grigore
    2. CO@Adrian Grigore: I can refactor the N enum's values into an abstract class (with the Accept(IVisitor) method) plus N subclasses. The IVisitor will have N Visit methods (one method for every implementation of the abstract class). Thanks to the visitor, I can define polymophics behaviour outside the domain layer, without importing stranger object into the domain (like business or presentation objects). :)
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