Question

I’d like to construct a message with unknown length or number of arguments. I took a simple template like

template <typename T> class Argument { public:     int size;     int type;     T data; }; 

and with some overloaded

addMessage (int value) {     Argument<int> *a = new Argument<int>;     vec.push_back(a); } 

(same for string and so on) I try to push it all into one vector. I tried

std::vector<Argument* > vec; std::vector<Argument<typename T>* > vec; std::vector<Argument<>* > vec; 

but nothing of this seems to work. Is there a way to do this? Thanks in advance.

Answer 1

Option 1 : make sure that all different types of arguments derive from a base class and use pointers to that class. Note that this option is risky in terms of memory management. You might want to make it safer by using boost::shared_ptr instead of pointers. Otherwise, you must manually clean up when an item is being removed from the vector.

Option 2 (my personal favorite) : use Boost.Variant to make a typedef of all possible argument types and use that typedef as the argument type in std::vector

typedef boost::variant<ArgumentType1, ArgumentType2, ArgumentType3> ArgumentType; std::vector<ArgumentType> vec;