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[C++] Container for any type

kloffy · 2006-03-05T06:16:15

I've been playing around with templates lately and I ran into a problem. Lets say I wanted a Container to hold any type, like boost::any. One way to do this would be like that: /* Abstract base class for my container */ class CAnyBase { public: virtual void* get()=0; virtual const type_info& type()=0; }; /* Template class to hold the object */ template<typename TType> class CAnyType : public CAnyBase { public: CAnyType(TType _object){ object = _object;} ~CAnyType(){} virtual void* get() { return &object; } virtual const type_info& type() { return typeid(TType); } private: TType object; }; /* Wrapper class */ class CAnyTypeWrapper { public: template<typename TType> CAnyTypeWrapper(TType _object){ object = new CAnyType<TType>(_object);} ~CAnyTypeWrapper(){} template<typename TType> bool put(TType& temp) { if(typeid(TType)==object->type()) { temp = *((TType*)object->get()); return 1;} return 0; } private: CAnyBase* object; }; Now this works pretty nicely. You can do things like: string str = "hi"; vector<CAnyTypeWrapper*> anyvector; anyvector.push_back(new CAnyTypeWrapper(str)); //StdStrings anyvector.push_back(new CAnyTypeWrapper(1)); //Integers anyvector.push_back(new CAnyTypeWrapper('c')); //Chars etc. However, if I wanted to overload the stream operators to work with my CAnyTypeWrapper for example, the only way I can come up with is this: friend istream& operator >>(istream &is,CAnyTypeWrapper &obj) { if(typeid(int) == obj.object->type()) { is >> *((int*)obj.object->get()); } else if(typeid(float) == obj.object->type()) { is >> *((float*)obj.object->get()); } else if(typeid(double) == obj.object->type()) { is >> *((double*)obj.object->get()); } else if(typeid(char) == obj.object->type()) { is >> *((char*)obj.object->get()); } else if(typeid(bool) == obj.object->type()) { is >> *((bool*)obj.object->get()); } else if(typeid(int*) == obj.object->type()) { is >> *((int*)obj.object->get()); } else if(typeid(float*) == obj.object->type()) { is >> *((float*)obj.object->get()); } else if(typeid(double*) == obj.object->type()) { is >> *((double*)obj.object->get()); } else if(typeid(char*) == obj.object->type()) { is >> *((char*)obj.object->get()); } else if(typeid(bool*) == obj.object->type()) { is >> *((bool*)obj.object->get()); } else if(typeid(string) == obj.object->type()) { is >> *((string*)obj.object->get()); } //And so on... return is; } friend ostream& operator <<(ostream &os,const CAnyTypeWrapper &obj) { if(typeid(int) == obj.object->type()) { os << *((int*)obj.object->get()); } else if(typeid(float) == obj.object->type()) { os << *((float*)obj.object->get()); } else if(typeid(double) == obj.object->type()) { os << *((double*)obj.object->get()); } else if(typeid(char) == obj.object->type()) { os << *((char*)obj.object->get()); } else if(typeid(bool) == obj.object->type()) { os << *((bool*)obj.object->get()); } else if(typeid(int*) == obj.object->type()) { os << *((int*)obj.object->get()); } else if(typeid(float*) == obj.object->type()) { os << *((float*)obj.object->get()); } else if(typeid(double*) == obj.object->type()) { os << *((double*)obj.object->get()); } else if(typeid(char*) == obj.object->type()) { os << *((char*)obj.object->get()); } else if(typeid(bool*) == obj.object->type()) { os << *((bool*)obj.object->get()); } else if(typeid(string) == obj.object->type()) { os << *((string*)obj.object->get()); } //And so on... return os; } Which, of course, isn't very nice. Is there a better way to do this?

General and Gameplay Programming Programming

Started by kloffy March 04, 2006 10:48 AM

9 comments, last by kloffy 18 years, 1 month ago

kloffy

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March 05, 2006 06:16 AM

I've got another short question: Is this a good way of implementing an unsafe cast for CAnyTypeWrapper?

template<typename TType> TType unsafe_cast(CAnyTypeWrapper &obj) { 	return *((TType*)((CAnyType<TType>*)obj.object->get())); }

To allow access to object you'd have to make it a friend function of CAnyTypeWrapper. A call would look like that:

CAnyTypeWrapper any(5);int i = unsafe_cast<int>(any);

[C++] Container for any type

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