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POOverloading with a class hierarchy - most derived not used
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copied!<p><strong>The problem</strong></p> <p>I am trying to avoid code that looks like the following:</p> <pre><code>If(object Is Man) Return Image("Man") ElseIf(object Is Woman) Return Image("Woman") Else Return Image("Unknown Object") </code></pre> <p>I thought I could do this through method overloading, but it always picks the least derived type, I assume this is because the overloading is determined at compile time (unlike overriding), and therefore only the base class can be assumed in the following code:</p> <p><strong>Code structure:</strong></p> <pre><code>NS:Real RealWorld (Contains a collection of all the RealObjects) RealObject Person Man Woman NS:Virtual VirtualWorld (Holds a reference to the RealWorld, and is responsible for rendering) Image (The actual representation of the RealWorldObject, could also be a mesh..) ArtManager (Decides how an object is to be represented) </code></pre> <p><strong>Code Implementation (key classes):</strong></p> <pre><code>class VirtualWorld { private RealWorld _world; public VirtualWorld(RealWorld world) { _world = world; } public void Render() { foreach (RealObject o in _world.Objects) { Image img = ArtManager.GetImageForObject(o); img.Render(); } } } static class ArtManager { public static Image GetImageForObject(RealObject obj)// This is always used { Image img = new Image("Unknown object"); return img; } public static Image GetImageForObject(Man man) { if(man.Age < 18) return new Image("Image of Boy"); else return new Image("Image of Man"); } public static Image GetImageForObject(Woman woman) { if (woman.Age < 70) return new Image("Image of Woman"); else return new Image("Image of Granny"); } } </code></pre> <p><strong>My scenario:</strong> Essentially I am creating a game, and want to decouple real-world classes (such as a man), from on-screen classes (an image of a person). The real world object should have no knowledge of it's on-screen representation, the representation will need to be aware of the real object (to know how old the man is, and therefore how many wrinkles are drawn). I want to have the fallback where if a RealObject is of an unknown type, it still displays something (like a big red cross).</p> <p>Please note that this code is not what i'm using, it's a simplified version to keep the question clear. I may need to add details later if applicable, I'm hoping the solution to this code will also work in the application.</p> <p>What's the most elegant way to solve this? - Without the RealObject itself holding information on how it should be represented. The XNA game is a proof of concept which is very AI heavy, and if it proves doable, will be changed from 2D to 3D (probably supporting both for lower end computers).</p>

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