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    <p>I think <a href="https://stackoverflow.com/questions/5128475/managing-diverse-classes-with-a-central-manager-without-rtti/5128502#5128502">bdonlan's suggestion</a> is good, but requiring each module type to declare a distinct <code>INTERFACE_ID</code> is a maintenance headache. The distinctness can be accomplished automatically by having each module type declare a static object and using its address as the ID:</p> <pre><code>struct IModuleFoo : public IModuleBase { static char distinct_; // Exists only to occupy a unique address static const void *INTERFACE_ID; virtual void foo() = 0; }; // static members need separate out-of-class definitions char IModuleFoo::distinct_; const void *IModuleFoo::INTERFACE_ID = &amp;distinct_; </code></pre> <p>In this case we are using <code>void *</code> as the interface ID type, instead of <code>int</code> or an enumerated type, so the types in some other declarations will need to change.</p> <p>Also, due to quirks in C++, the <code>INTERFACE_ID</code> values, despite being labelled <code>const</code>, are not "constant enough" to be used for <code>case</code> labels in <code>switch</code> statements (or array size declarations, or a handful of other places), so you would need to change the <code>switch</code> statement to an <code>if</code>. As described in section 5.19 of the standard, a <code>case</code> label requires an <em>integral constant-expression</em>, which roughly speaking is something the compiler can determine just from looking at the current translation unit; while <code>INTERFACE_ID</code> is a mere <em>constant-expression</em>, whose value cannot be determined until link time.</p>
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    1. POManaging diverse classes with a central manager without RTTI
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    1. COThis is an interesting idea. However, what is the advantage of this approach over using RTTI in the first place?
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    2. CO@rocktale: There's essentially no advantage, apart from possibly saving a small amount of space by only keeping meta-information on those classes we expressly want to manage instead of all classes that have a virtual method. RTTI's `dynamic_cast` is actually more powerful than what we have here because it allows testing of any "level" of downcast (useful if you have a multi-level hierarchy of module types), though it's possibly slightly slower.
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    3. COThat's what I thought, too. I have no reason to not use RTTI's `dynamic_cast` here. Nonetheless, I learned a lot from your answers so far.
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