std::reference_wrapper<T>::reference_wrapper
< cpp | utility | functional | reference wrapper
template< class U > reference_wrapper( U&& x ) noexcept(/*see below*/) ; |
(1) | |
reference_wrapper( const reference_wrapper& other ) noexcept; |
(2) | |
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 only participates in overload resolution 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)
noexcept specification:
where noexcept(noexcept(FUN(std::declval<U>())))
FUN
is the set of imaginary functions described in the description above.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 interferes with overload resolution in some cases
|
replaced with a constructor template |