std::reference_wrapper::operator()

C++

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Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

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Strings library

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Algorithms library

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Numerics library

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Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

Utilities library

Type support (basic types, RTTI, type traits)
Dynamic memory management
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bitset
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rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=
Comparisons (C++20)
strong_order weak_order partial_order strong_equal weak_equal	strong_ordering weak_ordering partial_ordering strong_equality weak_equality	is_eqis_neqis_ltis_lteqis_gtis_gteq
common_comparison_category
Common vocabulary types
pair tuple (C++11) apply (C++17) make_from_tuple (C++17)	optional (C++17) any (C++17) variant (C++17)
Swap, forward and move
swap
exchange (C++14)
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Function objects

Function wrappers function (C++11) mem_fn (C++11) bad_function_call (C++11)	Bind bind (C++11) is_bind_expression (C++11) is_placeholder (C++11) _1, _2, _3, ... (C++11)
Function invocation invoke (C++17) Identity function object identity (C++20)	Reference wrappers reference_wrapper (C++11) refcref (C++11)(C++11)
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
default_searcher (C++17)
boyer_moore_searcher (C++17)
boyer_moore_horspool_searcher (C++17)
Old binders and adaptors
unary_function (until C++17) binary_function (until C++17) ptr_fun (until C++17) pointer_to_unary_function (until C++17) pointer_to_binary_function (until C++17) mem_fun (until C++17) mem_fun_tmem_fun1_tconst_mem_fun_tconst_mem_fun1_t (until C++17)(until C++17)(until C++17)(until C++17) not1 (until C++20) not2 (until C++20)	binder1stbinder2nd (until C++17)(until C++17) bind1stbind2nd (until C++17)(until C++17) mem_fun_ref (until C++17) mem_fun_ref_tmem_fun1_ref_tconst_mem_fun_ref_tconst_mem_fun1_ref_t (until C++17)(until C++17)(until C++17)(until C++17) unary_negate (until C++20) binary_negate (until C++20)

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.

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)