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    copied!<p>Hopefully, 76 lines of code speak more than a few words - (using C++11 version of these features instead of the boost ones, but they're pretty much the same anyway)</p> <p>I would put the definition of the <em>factory(ies)</em> and the definition of the <em>creators</em> in the same (or nearby) scope, so that each of the creators can "see" any of their dependent factories - avoiding the need to pass factories around too much, and avoiding singletons</p> <p>Cars &amp; Sirens:</p> <pre><code>class ISiren {}; class Siren : public ISiren { public: Siren() { std::cout &lt;&lt; "Siren Created" &lt;&lt; std::endl; } }; class ICar{}; class EstateCar : public ICar { public: EstateCar() { std::cout &lt;&lt; "EstateCar created" &lt;&lt; std::endl;} }; class PoliceCar : public ICar { std::shared_ptr&lt;ISiren&gt; siren; public: PoliceCar( std::shared_ptr&lt;ISiren&gt; siren) : siren( siren ) { std::cout &lt;&lt; "PoliceCar created" &lt;&lt; std::endl; } }; </code></pre> <p>Factories:</p> <pre><code>typedef std::function&lt; std::shared_ptr&lt;ICar&gt; () &gt; CreatorType; class CarFactory { std::map&lt;std::string, CreatorType&gt; creators; public: void AddFactory( std::string type, CreatorType func ) { creators.insert( std::make_pair(type, func) ); } std::shared_ptr&lt;ICar&gt; CreateCar( std::string type ) { CreatorType&amp; create( creators[type] ); return create(); } }; class SirenFactory { public: // Simple factory creating 1 siren type just for brevity std::shared_ptr&lt;ISiren&gt; CreateSiren() { return std::make_shared&lt;Siren&gt;(); } }; </code></pre> <p>"Factory Root" (main function, wherever factories are defined) :</p> <pre><code>int main() { CarFactory car_factory; // Car factory unaware of Siren factory SirenFactory siren_factory; auto EstateCarLambda = []() { return std::make_shared&lt;EstateCar&gt;(); }; // Estate car lambda knows nothing of the Siren Factory auto PoliceCarLambda = [&amp;siren_factory]() { return std::make_shared&lt;PoliceCar&gt;( siren_factory.CreateSiren() ); }; // Police car creation lambda using the Siren Factory car_factory.AddFactory( "EstateCar", EstateCarLambda ); car_factory.AddFactory( "PoliceCar", PoliceCarLambda ); std::shared_ptr&lt;ICar&gt; car1 = car_factory.CreateCar( "EstateCar" ); std::shared_ptr&lt;ICar&gt; car2 = car_factory.CreateCar( "PoliceCar" ); } </code></pre>
 

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