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  1. PO
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    <p>One way to do this would be:</p> <pre><code>class Base { public: Base(); virtual ~Base(); virtual void doSomething(); }; class DerivedOne : public Base { public: DerivedOne(); void doSomethingElse(int a,struct b); }; class DerivedTwo : public Base { public: DerivedTwo(); virtual void doSomething(); }; </code></pre> <p>You could then use <code>dynamic_cast</code> to determine the type at runtime since you seem to have a type-conditional expression someplace in <code>SomeClass</code>. The methods are not equal and fundamentally distinct. Also, <code>DerivedOne::doSomething</code> would hide <code>Base::doSomething</code>.</p> <p><strong>Update</strong></p> <p>As the others had already stated, it's often a bad smell if your program relies on type-conditional expressions. Since your example does not have enough context to offer appropriate solutions, it's hard for us to help you in this regard. If you are interested in removing the type-conditional, one of many potential solutions to this problem would be:</p> <pre><code>class Base { public: Base(); virtual ~Base(); virtual void doSomething(); }; class DerivedOne : public Base { public: DerivedOne(); // ... virtual void doSomething(); // &lt;&lt; no parameters required. // they have moved to member data: private: int a; b another; }; class DerivedTwo : public Base { public: DerivedTwo(); virtual void doSomething(); }; </code></pre> <p>then you could remove the type-conditional expression from your program. If you'd like help in this regard, feel free to ask here or open a new question if you feel it is more appropriate.</p>
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    1. POWhat should be my virtual function's prototype?
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    1. USjustin
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    1. POWhat should be my virtual function's prototype?
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    1. COType conditional code in the base class to test which derived class the instance is is a pretty major design flaw.
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      1. USDavid Heffernan
    2. CO@DavidHeffernan I agree with you *but* that's not the case here; the OP specified the type-condition occurs in the implementation of `SomeClass`.
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      1. USjustin
    3. COIt amounts to much the same since the target of the function call is a Base*. Anyway, I just wanted to point out that although this is the accepted answer, the original question and this direct answer have the whiff of bad design.
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      1. USDavid Heffernan
 

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