I'm attempting to specialize a function template but I'm getting the following error :
bar.cpp:12:39: error: template-id ‘getValue<>’ for ‘std::variant<int, double> Test::getValue(const string&)’ does not match any template declaration
12 | template <> std::variant<int, double> Test::getValue(const std:: string& name) {
| ^~~~
bar.cpp:7:29: note: candidate is: ‘template<class T> T Test::getValue(const string&) const’
7 | template <typename T> T getValue(const std::string& name) const;
| ^~~~~~~~
Yet I can't find why this is the case, as far as I see I'm respecting the method signature.
#include <iostream>
#include <unordered_map>
#include <variant>
class Test {
Test();
template <typename T> T getValue(const std::string& name) const;
std::unordered_map<std::string, std::variant<int, double>> dict_;
};
template <> std::variant<int, double> Test::getValue(const std:: string& name) {
// ... do things
}
CodePudding user response：
Template parameters need to be explicitely defined.
template <> std::variant<int, double> Test::getValue<std::variant<int, double>>(const std::string& name) const {
std::cout << "Hello" << std::endl;
}
CodePudding user response：
Your specialized member function misses the const qualifier, which makes it inconsistent with the primary template inside the class.
This should work
template <>
std::variant<int, double> Test::getValue(const std:: string& name) const
//^^^^
{ }