std::reference_wrapper<T>::operator()
From cppreference.com
< cpp | utility | functional | reference wrapper
template< class... ArgTypes > typename std::result_of<T&(ArgTypes&&...)>::type |
(since C++11) (until C++17) |
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| template< class... ArgTypes > std::invoke_result_t<T&, ArgTypes...> |
(since C++17) (constexpr since C++20) |
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Calls the Callable object, reference to which is stored, as if by INVOKE(get(), std::forward<ArgTypes>(args)...). This function is available only if the stored reference points to a Callable object.
T must be a complete type.
Parameters
| args | - | arguments to pass to the called function |
Return value
The return value of the called function.
Exceptions
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May throw implementation-defined exceptions. |
(since C++11) (until C++17) |
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noexcept specification:
noexcept(std::is_nothrow_invocable_v<T&, ArgTypes...>) |
(since C++17) |
Example
Run this code
#include <functional> #include <iostream> void f1() { std::cout << "reference to function called\n"; } void f2(int n) { std::cout << "bind expression called with " << n << " as the argument\n"; } int main() { std::reference_wrapper<void()> ref1 = std::ref(f1); ref1(); auto b = std::bind(f2, std::placeholders::_1); auto ref2 = std::ref(b); ref2(7); auto c = []{ std::cout << "lambda function called\n"; }; auto ref3 = std::ref(c); ref3(); }
Output:
reference to function called bind expression called with 7 as the argument lambda function called
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 3764 | C++17 | operator() is not noexcept | propagate noexcept |
See also
| accesses the stored reference (public member function) |