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std::get (std::variant)

Defined in header `<variant>`
	(1)	(since C++17)
template <std::size_t I, class... Types> constexpr std::variant_alternative_t< I, std::variant<Types...> >& get(std::variant<Types...>& v);
template <std::size_t I, class... Types> constexpr std::variant_alternative_t< I, std::variant<Types...> >&& get(std::variant<Types...>&& v);
template <std::size_t I, class... Types> constexpr std::variant_alternative_t< I, std::variant<Types...> > const& get(const std::variant<Types...>& v);
template <std::size_t I, class... Types> constexpr std::variant_alternative_t< I, std::variant<Types...> > const&& get(const std::variant<Types...>&& v);
			(2)	(since C++17)
template <class T, class... Types> constexpr T& get(std::variant<Types...>& v);
template <class T, class... Types> constexpr T&& get(std::variant<Types...>&& v);
template <class T, class... Types> constexpr const T& get(const std::variant<Types...>& v);
template <class T, class... Types> constexpr const T&& get(const std::variant<Types...>&& v);

1) Index-based value accessor: If v.index() == I, returns a reference to the value stored in v. Otherwise, throws std::bad_variant_access. The call is ill-formed if I is not a valid index in the variant or if T_I is a (possibly cv-qualified) type void.

2) Type-based value accessor: If v holds the alternative T, returns a reference to the value stored in v. Otherwise, throws std::bad_variant_access. The call is ill-formed if T is not a unique element of Types... or if T is a (possibly cv-qualified) type void.

Parameters

I	-	index to look up
Type	-	unique type to look up
v	-	a variant

Return value

Reference to the value stored in the variant.

Exceptions

1,2) Throws std::bad_variant_access on errors.

Example

#include <variant>
#include <string>
 
int main()
{
    std::variant<int, float> v{12}, w;
    int i = std::get<int>(v);
    w = std::get<int>(v);
    w = std::get<0>(v); // same effect as the previous line
 
//  std::get<double>(v); // error: no double in [int, float]
//  std::get<3>(v);      // error: valid index values are 0 and 1
 
    try {
      std::get<float>(w); // w contains int, not float: will throw
    }
    catch (std::bad_variant_access&) {}
}

get_if (C++17)	obtains a pointer to the value of a pointed-to variant given the index or the type (if unique), returns null on error (function template)
std::get(std::tuple)	tuple accesses specified element (function template)
std::get(std::array)	accesses an element of an `array` (function template)
std::get(std::pair) (C++11)	accesses an element of a `pair` (function template)

std::get (std::variant)

Parameters

Return value

Exceptions

Example

See also