Modern C++ Programming Cookbook

There's more...

In the preceding implementation, the map is a local static to the virtual function, but it can also be a member of the class or even a global. The following implementation has the map defined as a static member of the class, and the objects are not created based on the format name, but on the type information, as returned by the typeid operator:

    struct IImageFactoryByType    {      virtual std::shared_ptr<Image> Create(std::type_info const & type)       = 0;    };    struct ImageFactoryByType : public IImageFactoryByType    {      virtual       std::shared_ptr<Image> Create(std::type_info const & type)       override      {        auto it = mapping.find(&type);        if (it != mapping.end())          return it->second();        return nullptr;      }    private:      static std::map< std::type_info const ...