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PODouble dispatch/multimethods in C++
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  1. PODouble dispatch/multimethods in C++
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    copied!<p>I have a question on C++ double dispatch. In the code below, I want the results from the second set to match the results from the first set. </p> <p>I don't know the actual type (unless I try dynamic_cast) but I do know that the object inherited from the BaseClass type. What is the most efficient (performance-wise) way to accomplish this?</p> <p>After googling around for a while I found out about double dispatch and the loki multimethods. The problem I have with the Shape examples is that in my application, Processor and BaseClass are entirely independent and don't have a common method that they can call in each other. Secondly, there is only one Processor (i.e. nothing inherits from it).</p> <p>Thanks for any help.</p> <pre><code>#include &lt;iostream&gt; #include &lt;string&gt; using namespace std; class BaseClass{ public: BaseClass(){} virtual void myFunction(){cout &lt;&lt; "base myFunction called" &lt;&lt; endl;} }; class Derived1: public BaseClass{ public: Derived1():BaseClass(){} void myFunction(){cout &lt;&lt; "Derived1 myFunction called" &lt;&lt; endl;} }; class Derived2: public BaseClass{ public: Derived2():BaseClass(){} void myFunction(){cout &lt;&lt; "Derived2 myFunction called" &lt;&lt; endl;} }; class Derived3: public BaseClass{ public: Derived3():BaseClass(){} void myFunction(){cout &lt;&lt; "Derived3 myFunction called" &lt;&lt; endl;} }; class Processor{ public: Processor(){} virtual void processObj(BaseClass* bc){cout &lt;&lt; "got a base object" &lt;&lt; endl; bc-&gt;myFunction();} virtual void processObj(Derived1* d1){cout &lt;&lt; "got a derived1 object" &lt;&lt; endl; d1-&gt;myFunction();} virtual void processObj(Derived2* d2){cout &lt;&lt; "got a derived2 object" &lt;&lt; endl; d2-&gt;myFunction(); } }; int main() { BaseClass *bcp=new BaseClass(); Derived1 *dc1p=new Derived1(); Derived2 *dc2p=new Derived2(); Derived3 *dc3p=new Derived3(); Processor p;//can also use Processor* p = new Processor() //first set results p.processObj(bcp); p.processObj(dc1p); p.processObj(dc2p); p.processObj(dc3p); BaseClass *bcp1=bcp; BaseClass *dc1p1=dc1p; BaseClass *dc2p1=dc2p; BaseClass *dc3p1=dc3p; //second set results p.processObj(bcp1); p.processObj(dc1p1); p.processObj(dc2p1); p.processObj(dc3p1); return 0; } </code></pre>
 

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