std::variant<Types...>:: visit

Applies the visitor vis (a Callable that can be called with any combination of types from the variant) to the variant held by self .

Given type V as decltype ( std:: forward_like < Self > ( std:: declval < variant > ( ) ) ) , the equivalent call is:

Parameters

Return value

Exceptions

Only throws if the call to std :: visit throws.

Notes

Example

#include <print>
#include <string>
#include <string_view>
#include <variant>
struct Base {};
struct Derived : Base {};
// helper type for the visitor
template<class... Ts>
struct overloads : Ts... { using Ts::operator()...; };
// the variant to visit
using var_t = std::variant<int, std::string, Derived>;
int main()
{
    const auto visitor = overloads
    {
        [](int i){ std::print("int = {}\n", i); },
        [](std::string_view s){ std::println("string = “{}”", s); },
        [](const Base&){ std::println("base"); }
    };
    const var_t var1 = 42, var2 = "abc", var3 = Derived();
#if (__cpp_lib_variant >= 202306L)
    var1.visit(visitor);
    var2.visit(visitor);
    var3.visit(visitor);
#else
    std::visit(visitor, var1);
    std::visit(visitor, var2);
    std::visit(visitor, var3);
#endif
}

int = 42
string = “abc”
base

See also