[c++] overriding template class
Author
i've got a template wit the following function definition:
template <class T>
Packet& operator &(Packet& packet, T& data)
this is a non-intrusive template function so i can add any class to a 'packet', but i want to be able to override this version with any custom version eg:
template <class T>
Packet& operator &(Packet& packet, std::string& data)
but when i do this, the base template version gets called.
Any ideas on how to do this? I think they do it in boost library somehow.
Quote:template <class T>Packet& operator &(Packet& packet, T& data)template <class T>Packet& operator &(Packet& packet, std::string& data)
The latter is not a specialization of the former, as you still have an unbound template parameter T. You have to either do a correct specialization or use the regular function overloading:
// Either:template <>Packet& operator &<std::string>(Packet& packet, std::string& data);// Or simply:Packet& operator &(Packet& packet, std::string& data);There are some gotchas you need to be vary of, though. Please read the following articles by Herb Sutter:
http://www.gotw.ca/gotw/049.htm
http://www.gotw.ca/publications/mill17.htm
Quote:// Either:template <>Packet& operator &<std::string>(Packet& packet, std::string& data);// Or simply:Packet& operator &(Packet& packet, std::string& data);
im not sure if this is mentioned in one of the two gotcha links you posted but the second one doesnt actualy do template specialization it defines a non-template overload of the operator. :-)
Yes, as I said. The point is that it is semantically almost equivalent, and, as explained in the second link, usually the better alternative of the two.
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