std::reference_wrapper::operator()

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

Calls the Callable object, reference to which is stored. This function is available only if the stored reference points to a Callable object.

Parameters

args - arguments to pass to the called function

Return value

The return value of the called function.

Exceptions

(none)

Example

#include <iostream>
#include <functional>

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

See also

accesses the stored reference
(public member function)