std::variant<Types...>::index
From cppreference.com
constexpr std::size_t index() const noexcept;
|
(since C++17) | |
Returns the zero-based index of the alternative that is currently held by the variant.
If the variant is valueless_by_exception, returns variant_npos.
Example
Run this code
#include <iostream>
#include <string>
#include <variant>
int main()
{
std::variant<int, std::string> v = "abc";
std::cout << "v.index = " << v.index() << '\n';
v = {};
std::cout << "v.index = " << v.index() << '\n';
}
Output:
v.index = 1
v.index = 0
See also
(C++17) |
checks if a variant currently holds a given type (function template) |
(C++17) |
reads the value of the variant given the index or the type (if the type is unique), throws on error (function template) |