std::get_if
Defined in header <variant> | ||
|---|---|---|
| (1) | (since C++17) | |
template <std::size_t I, class... Types>
constexpr std::add_pointer_t<
std::variant_alternative_t<I, std::variant<Types...>>
> get_if(std::variant<Types...>* pv) noexcept;
| ||
template <std::size_t I, class... Types>
constexpr std::add_pointer_t<
const std::variant_alternative_t<I, variant<Types...>>
> get_if(const std::variant<Types...>* pv) noexcept;
| ||
| (2) | (since C++17) | |
template <class T, class... Types> constexpr std::add_pointer_t<T> get_if(std::variant<Types...>* pv) noexcept; | ||
template <class T, class... Types> constexpr std::add_pointer_t<const T> get_if(const std::variant<Types...>* pv) noexcept; |
1) Index-based non-throwing accessor: If
pv is not a null pointer and pv->index() == I, returns a pointer to the value stored in the variant pointed to by pv. Otherwise, returns a null pointer value. The call is ill-formed if I is not a valid index in the variant.
2) Type-based non-throwing accessor: Equivalent to (1) with
I being the zero-based index of T in Types.... The call is ill-formed if T is not a unique element of Types....Parameters
| I | - | index to look up |
| Type | - | unique type to look up |
| pv | - | pointer to a variant |
Return value
Pointer to the value stored in the pointed-to variant or null pointer on error.
Example
#include <variant>
#include <iostream>
int main()
{
std::variant<int, float> v{12};
if(auto pval = std::get_if<int>(&v))
std::cout << "variant value: " << *pval << '\n';
else
std::cout << "failed to get value!" << '\n';
}Output:
variant value: 12
See also
|
(C++17) | reads the value of the variant given the index or the type (if the type is unique), throws on error (function template) |
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