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# std::get_if

From cppreference.com
< 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) |  |
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) |  |
| (2) | (since C++17)
template <class T, class... Types> constexpr std::add_pointer_t<T> get_if(variant<Types...>* pv) |  |
template <class T, class... Types> constexpr std::add_pointer_t<const T> get_if(const variant<Types...>* pv) |  |

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 or if `T_I` is a (possibly cv-qualified) type `void`.
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...` or if `T_I` is a (possibly cv-qualified) type `void`.

### [edit] Parameters

I | - | index to look up
Type | - | unique type to look up
pv | - | pointer to a variant

### [edit] Return value

Pointer to the value stored in the pointed-to variant or null pointer on error.

### [edit] Exceptions

1,2)
`noexcept` specification:
noexcept

### [edit] 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

### [edit] 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) [edit]

Retrieved from "http://en.cppreference.com/mwiki/index.php?title=cpp/utility/variant/get_if&oldid=91674"
Category:

- unconditionally noexcept

Hidden categories:

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