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std::reference_wrapper<T>::operator()

template< class... ArgTypes >
typename std::result_of<T&(ArgTypes&&...)>::type
    operator() ( ArgTypes&&... args ) const;

(since C++11)
(until C++17)

template< class... ArgTypes >
std::invoke_result_t<T&, ArgTypes...>
    operator() ( ArgTypes&&... args ) const noexcept(/* see below */);

(since C++17)
(until C++20)

template< class... ArgTypes >
constexpr std::invoke_result_t<T&, ArgTypes...>
    operator() ( ArgTypes&&... args ) const noexcept(/* see below */);

(since C++20)

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

May throw implementation-defined exceptions.	(since C++11) (until C++17)
`noexcept` specification: `noexcept(std::is_nothrow_invocable_v<T&, ArgTypes...>)`	(since C++17)

Example

#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.