Loading classes dynamically in C++
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I have a data file which tells me what class to load. Is there a way to pass in a string with the name of the class and get a pointer to that type? In C#, I would just use reflection to do this. Does C++ have an equivalent? Or would you advise I just use a scripting language for these classes?
Thanks.
-Nick
C++ can't refer to types by name; nor does it support reflection. You'll have to store the correspondance in some data structure (e.g. a std::map). What you are looking for is called a Factory (Object Factory/Abstract Factory/Generic Factory/Factory Pattern...)
You need what is called Pluggable Factories. Here's some basic code to do it, should mostly be self-explanatory:
I just grabbed that code really quickly from all my helper code I use for my projects. You seem experienced with programming, so hopefully you understand what it's doing. If not, just ask and I'll explain in further detail.
Edit: here is an article discussing them in detail.
typedef std::string ObjectType;template<class Base>class CreatorBase{public: virtual ~CreatorBase() {} virtual Base * Create() const = 0;};template<class Product, class Base>class Creator : public CreatorBase<Base>{public: virtual Base * Create() const {return new Product;}};template<class Base>class Factory{public: Base * Create(ObjectType type); bool Register(ObjectType type, CreatorBase<Base> * pCreator);private: typedef std::map<ObjectType, CreatorBase<Base> *> CreatorMap; CreatorMap m_creatorMap;};template<class Base>bool Factory<Base>::Register(ObjectType type, CreatorBase<Base> * pCreator){ CreatorMap::iterator it = m_creatorMap.find(type); if (it != m_creatorMap.end()) { delete pCreator; return false; } m_creatorMap[type] = pCreator; return true;}template<class Base>Base * Factory<Base>::Create(ObjectType type){ CreatorMap::iterator it = m_creatorMap.find(type); if (it == m_creatorMap.end()) return NULL; CreatorBase<Base> * pCreator = (*it).second; return pCreator->Create();}I just grabbed that code really quickly from all my helper code I use for my projects. You seem experienced with programming, so hopefully you understand what it's doing. If not, just ask and I'll explain in further detail.
Edit: here is an article discussing them in detail.
you could dynamically load in .o or .dll (whatever os your using) files and have provided in them entry and exit classes/functions (i.e a static function to return a new instance of your class).
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