std::reference_wrapper::operator()

 

C++

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Technical Specifications

 

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Function objects

Function wrappers function (C++11) mem_fn (C++11) bad_function_call (C++11)	Partial function application bind_front (C++20) bind (C++11) is_bind_expression (C++11) is_placeholder (C++11) _1, _2, _3, ... (C++11)
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Operator wrappers
plus minus negate multiplies divides modulus logical_and logical_or logical_not	equal_to not_equal_to greater less greater_equal less_equal bit_and bit_or bit_xor bit_not (C++14)
Negators
not_fn (C++17)
Searchers
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Old binders and adaptors
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std::reference_wrapper

Member functions

reference_wrapper::reference_wrapper

reference_wrapper::operator=

reference_wrapper::getreference_wrapper::operator T&

reference_wrapper::operator()

Deduction guides(C++17)

 

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.

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

See also

getoperator T&

accesses the stored reference (public member function)