std::reference_wrapper<T>::reference_wrapper
| (1) | ||
template< class U > reference_wrapper( U&& x ) noexcept(/*see below*/) ; |
(until C++20) | |
template< class U > constexpr reference_wrapper( U&& x ) noexcept(/*see below*/) ; |
(since C++20) | |
| (2) | ||
reference_wrapper( const reference_wrapper& other ) noexcept; |
(until C++20) | |
constexpr reference_wrapper( const reference_wrapper& other ) noexcept; |
(since C++20) |
Constructs a new reference wrapper.
1) Converts
x to
T& as if by
T& t = std::forward<U>(x);, then stores a reference to
t. This overload participates in overload resolution only if
typename std::decay<U>::type is not the same type as
reference_wrapper 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;
2) Copy constructor. Stores a reference to
other.get().
Parameters
| x | - | an object to wrap |
| other | - | another reference wrapper |
Exceptions
1)
where
noexcept specification:
noexcept(noexcept(FUN(std::declval<U>())))
FUN is the set of imaginary functions described in the description above.
Example
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 2993 | C++11 | deleted reference_wrapper(T&&) constructor interfereswith overload resolution in some cases |
replaced with a constructor template |
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