std::experimental::optional::operator=
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< cpp | experimental | optional
| optional& operator=( std::nullopt_t ); |
(1) | (library fundamentals TS) |
| optional& operator=( const optional& other ); |
(2) | (library fundamentals TS) |
| optional& operator=( optional&& other ); |
(3) | (library fundamentals TS) |
| template< class U > optional& operator=( U&& value ); |
(4) | (library fundamentals TS) |
Assigns contents to the contained value.
1) If *this is in engaged state before the call, the contained value is destroyed by calling its destructor. *this is in disengaged state after the call.
2-3) Assigns the state of
other. * If both *this and
other are in disengaged states, the function has no effect. * If *this is in engaged state, but
other is not, then the contained value is destroyed by calling its destructor. *this is in disengaged state after the call. * If
other is in engaged state, then depending on whether *this is in engaged state, the contained value is either direct-constructed or assigned the contained value of other. The contained value is either copied (2), or moved (3).4) Depending on whether *this is in engaged state before the call, the contained value is either direct-constructed from
value or assigned value. T must be constructible and assignable from U, i.e. the following must hold:
std::is_constructible<T,U>::value == true && std::is_assignable<T,U>::value == trueContents |
[edit] Parameters
| other | - | another optional object whose contained value to assign
|
| value | - | value to assign to the contained value |
| Type requirements | ||
-T must meet the requirements of CopyAssignable and CopyConstructible in order to use overload (2).
| ||
-T must meet the requirements of MoveAssignable and MoveConstructible in order to use overload (3).
| ||
[edit] Return value
*this
[edit] Exceptions
1)
noexcept specification:
noexcept
2-4) Throws any exception thrown by the constructor or assignment operator of
T. If an exception is thrown, the initialization state of *this (and of other in case of (2) ) is unchanged, i.e. if the object was in engaged state, it is left in engaged state, and the other way round. The contents of value and the contained values of *this and other depend on the exception safety guarantees of the operation from which the exception originates (copy-constructor, move-assignment, etc.).3) Throws any exception thrown by the constructor or assignment operator
T. Has the following noexcept declaration: noexcept specification:
noexcept(std::is_nothrow_move_assignable<T>::value && std::is_nothrow_move_constructible<T>::value)
[edit] See also
| constructs the contained value in-place (public member function) |