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POC++: Identifying the type of the object
 

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    <p>I'm curious what constructs or language features, available in both the current C++ as well as in C++11, can be used to deduce the type of an object. An example:</p> <pre><code>class Base { }; class DerivA : public Base { }; class DerivB : public Base { }; void foo(Base* obj) { // Identify if `obj` is a `DerivA` or a `DerivB` } </code></pre> <p>This is an oversimplification. It would appear that rather than having a way to identify the type, the best solution is to have overloads of the function for the two derived types and do away with the base class.</p> <p>My real use case is one where one class is not interested in the exact type of the object (ie. just needs an implementation of <code>Base</code>) and another class needs to know exactly what implementation of <code>Base</code> the first class is using.</p> <p>This happens in a component-based game entity system. The base would be an <code>EntityState</code> and its derived types are <code>StandingState</code>, <code>DeadState</code>, etc. Class <code>Entity</code> is the one that only needs a generic <code>EntityState</code> object and class <code>EntityRepresentation</code> needs to know exactly what state the entity is in to decide whether to draw the "standing" animation or the "dead" animation, or whatever.</p> <hr> <p><strong>Edit:</strong> Of course, if possible, I'd like to implement the game in such a way that not even the entity representation needs to know the type of the entity state. If there's a way to do that, then I'd use it. :) I'll look into the visitor pattern.</p>
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    1. USPaul Manta
    1. USPaul Manta
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    1. COTry a search for RTTI.
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      1. USNemo
    2. COThis would seem like a good fit for [the Visitor Pattern](http://en.wikipedia.org/wiki/Visitor_pattern).
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    3. COYou can't do away with the Base class and still use polymorphism normally.
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      1. USDavid Thornley
 

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