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copied!<p>I would separate the conversion of strings to enum into a distinct object. This can easily be solved by a map btw. But error handling etc. is still something which neither D nor the factory should be worried about.</p> <p>Then either D calls the converter to get its enum, or it is already converted beforehand, so D only needs to pass the enum to the factory. (Btw the factory would better use a map too instead of a switch internally).</p> <p>This raises the question: do you actually need the enums at all (in places other than D and the factory)? If not, maybe the enum could be left out of the picture and you could use a map to convert directly from strings to types (i.e. - since C++ doesn't support dynamic class loading - to function objects which create the necessary concrete type instances for you). A rough example (I don't have an IDE to test it so bear with me if there are any errors in it):</p> <pre><code>// Function type returning a pointer to B typedef (B*)(*func)() StaticConstructor; // Function creating instances of subclass E B* createSubclassE() { return new E(...); } // Function creating instances of subclass F B* createSubclassF() { return new F(...); } // Mapping from strings to constructor methods creating specific subclasses of B map<string, StaticConstructor> factoryMap; factoryMap["E"] = &createSubclassE; factoryMap["F"] = &createSubclassF; </code></pre> <p>Of course, the created instances should also be disposed of properly - in production code, the returned objects could be e.g. enclosed in an <code>auto_ptr</code>. But I hope this short example is enough to show you the basic idea. Here is <a href="http://www.newty.de/fpt/index.html" rel="nofollow noreferrer">a tutorial</a> if you want more...</p>

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