我会期待沿着这些线的东西：

#include <memory>
#include <string>
#include <functional>
#include <map>
#include <stdexcept>
#include <iostream>
// Declare an "interface" (abstract baseclass)
// this is the only knowledge your engine
// and client code will share
//
// But make sure client code compiles with an ABI
// compatible compiler!
//
class EntityItf
{
public:
    virtual ~EntityItf() = default;
    virtual void DoSomething() = 0;
};
using creation_function_t = std::function<std::unique_ptr<EntityItf>()>;
class /*dllexport */ EntityFactory
{
public:
    // Meyers singleton
    inline static EntityFactory& Instance()
    {
        static EntityFactory factory;
        return factory;
    }
    void RegisterCreationMethod(const std::string& entity_name, creation_function_t creation_function)
    {
        if ( m_factory_functions.find(entity_name) != m_factory_functions.end())
        {
            throw std::runtime_error{"An entity with that name has already been registered"};
        }
        m_factory_functions[entity_name] = creation_function;
    }
    std::unique_ptr<EntityItf> CreateEntity(const std::string& entity_name)
    {
        if ( m_factory_functions.find(entity_name) == m_factory_functions.end())
        {
            throw std::runtime_error{"Unknown entity name"};
        }
        return m_factory_functions[entity_name]();
    }
private:
    EntityFactory() = default;
    ~EntityFactory() = default;
    std::map<std::string,creation_function_t> m_factory_functions;
};
// Developer code
class MyEntity :
    public EntityItf
{
public:
    void DoSomething() override
    {
        std::cout << "Hello World!\n";
    }
};
int main()
{
    auto& factory = EntityFactory::Instance();
    factory.RegisterCreationMethod("MyEntity", []{ return std::make_unique<MyEntity>(); });
    auto my_entity = factory.CreateEntity("MyEntity");
    my_entity->DoSomething();
    return 0;
}

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