std::bad_variant_access (3) Linux Manual Page

std::bad_variant_access – std::bad_variant_access

Synopsis

Defined in header <variant>
class bad_variant_access : public std::exception (since C++17)
std::bad_variant_access is the type of the exception thrown in the following situations:
* std::get(std::variant) called with an index or type that does not match the currently active alternative
* std::visit called to visit a variant that is valueless_by_exception

Member functions

              constructs the bad_variant_access object
constructor (public member function)

 std::bad_variant_access ::bad_variant_access()

bad_variant_access() noexcept;

Constructs a new instance of std::bad_variant_access.

Parameters

(none)

Inherited from std::exception

Member functions

destructor destroys the exception object
             (virtual public member function of std::exception)
[virtual]

what returns an explanatory string
             (virtual public member function of std::exception)
[virtual]

Example

// Run this code

#include <variant>

#include <iostream>
int main()

{
    std::variant<int, float> v;
    v = 12;
    try {
        std::get<float>(v);
    } catch (const std::bad_variant_access &e) {
        std::cout << e.what() << '\n';
    }
}

Possible output:

  bad_variant_access

See also

std::get(std::variant) reads the value of the variant given the index or the type (if the type is unique), throws on error
                       (function template)
(C++17)
visit calls the provided functor with the arguments held by one or more variants
                       (function template)
(C++17)