std::reference_wrapper::reference_wrapper

 

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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++20)

 

	(1)
reference_wrapper( T& x ) noexcept; reference_wrapper( T&& x ) = delete;			(until C++20)
template< class U > reference_wrapper( U&& x ) noexcept(/*see below*/) ;			(since C++20)
reference_wrapper( const reference_wrapper& other ) noexcept;		(2)

Constructs a new reference wrapper.

1) Stores a reference to x. Construction from a temporary object is not allowed.	(until C++20)
1) Converts x to T& as if by T& t = std::forward<U>(x);, then stores a reference to t. This overload only participates in overload resolution if std::is_same_v<std::remove_cvref_t<U>, reference_wrapper> is false and the expression FUN(std::declval<U>()) is well-formed, where FUN names the set of imaginary functions void FUN(T&) noexcept; void FUN(T&&) = delete;	(since C++20)

2) Copy constructor. Stores a reference to other.get().

Parameters

x	-	an object to wrap
other	-	another reference wrapper

Exceptions

1) noexcept specification:   noexcept(noexcept(FUN(std::declval<U>()))) where FUN is the set of imaginary functions described in the description above.

(since C++20)

Notes

The pre-C++20 deleted constructor from T&& still participates in the formation of implicit conversion sequences, which can lead to unexpected results in overload resolution. The C++20 change (via LWG issue 2993) rectifies this problem.