std::reference_wrapper<T>::get, std::reference_wrapper<T>::operator T&
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< cpp | utility | functional | reference wrapper
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std::reference_wrapper
Member functions
reference_wrapper::getreference_wrapper::operator T&
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operator T& () const noexcept;
(1)
(since C++11) (constexpr since C++20)
T& get() const noexcept;
(2)
(since C++11) (constexpr since C++20)
Returns the stored reference.
Contents
[edit] Parameters
(none)
[edit] Return value
The stored reference.
[edit] Example
Run this code
#include <cassert> #include <functional> #include <map> #include <optional> #include <string_view> using Map = std::map <std::string_view, int>; using Opt = std::optional <std::reference_wrapper <Map::value_type>>; Opt find(Map& m, std::string_view s) { auto it = m.find(s); return it == m.end() ? Opt{} : Opt{*it}; } int main() { Map m{{"A", 1}, {"B", 2}, {"C", 3}}; if (auto opt = find(m, "C"); opt) opt->get().second = 42; // std::optional::operator->() returns reference to std::reference_wrapper, then // reference_wrapper::get() returns reference to map::value_type, i.e. std::pair assert (m["C"] == 42); }