# std::get_if

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< cpp‎ | utility‎ | variant

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

Run this code

    #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

std::get(std::variant) (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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