std::reference_wrapper<T>::operator() (3) - Linux Manuals

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

NAME

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

Synopsis

template< class... ArgTypes > (since C++11)
typename std::result_of<T&(ArgTypes&&...)>::type (until C++17)
operator() ( ArgTypes&&... args ) const;
template< class... ArgTypes >
std::invoke_result_t<T&, ArgTypes...> (since C++17)
operator() ( ArgTypes&&... args ) const;

Calls the Callable object, reference to which is stored. 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

(none)

Example

// Run this code

  #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