Generic Factory in C++
Factory pattern
A generic factory is a factory that can register any class type. It is very easy to write because we are allowed to use void pointers.
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#include <functional> class Factory { public: Factory() {} ~Factory() {} void Register(const std::string _key, const std::function<void *()> _creator) { m_creators[_key] = _creator; } template<typename ClassType> ClassType* Get(const std::string _key) const { return static_cast<ClassType *>(m_creators.at(_key)()); } private: std::map<std::string, std::function<void *()> > m_creators; }; |
Usage:
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int main() { Factory f; f.Register("Derived1", &BaseClass<Derived1>::CreateInterface); f.Register("Derived2", &BaseClass<Derived2>::CreateInterface); Derived1 *d1 = f.Get<Derived1>("Derived1"); Derived2 *d2 = f.Get<Derived2>("Derived2"); Derived1 *d2 = f.Get<Derived1>("Derived2"); // This also compiles!!! } |
As we are simply casting a void pointer, it is left to the developer to ensure the right class type is passed to Factory::Get function, which might not be the best practice.
