Diamond Inheritance
virtual keyword on multiple base class creates one and only copy
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#include <iostream> #include <memory> class RootOfAll { public: RootOfAll(){ std::cout << "RootOfAll" << std::endl; } ~RootOfAll(){ std::cout << "~RootOfAll" << std::endl; } }; // create one copy class MidLeft: virtual public RootOfAll{ public: MidLeft(){ std::cout << "MidLeft" << std::endl; } ~MidLeft(){ std::cout << "~MidLeft" << std::endl; } }; // create one copy class MidRight: virtual public RootOfAll{ public: MidRight(){ std::cout << "MidRight" << std::endl; } ~MidRight(){ std::cout << "~MidRight" << std::endl; } }; class TopClass: public MidLeft, public MidRight{ public: TopClass(){ std::cout << "TopClass" << std::endl; } ~TopClass(){ std::cout << "~TopClass" << std::endl; } }; int main() { // only shared pointers may use on abstract std::unique_ptr<TopClass> p { new TopClass{}}; return EXIT_SUCCESS; } |
