template< class ValueType, class... Args > std::decay_t<ValueType>& emplace( Args&&... args ); | (1) | (since C++17) |
template< class ValueType, class U, class... Args > std::decay_t<ValueType>& emplace( std::initializer_list<U> il, Args&&... args ); | (2) | (since C++17) |
Changes the contained object to one of type std::decay_t<ValueType> constructed from the arguments.
First destroys the current contained object (if any) by reset(), then:
std::decay_t<ValueType>, direct-non-list-initialized from std::forward<Args>(args)..., as the contained object. This overload only participates in overload resolution if std::is_constructible_v<std::decay_t<ValueType>, Args...> and std::is_copy_constructible_v<std::decay_t<ValueType>> are both true.std::decay_t<ValueType>, direct-non-list-initialized from il, std::forward<Args>(args)..., as the contained object. This overload only participates in overload resolution if std::is_constructible_v<std::decay_t<ValueType>, std::initializer_list<U>&, Args...> and std::is_copy_constructible_v<std::decay_t<ValueType>> are both true. | ValueType | - | contained value type |
| Type requirements | ||
-std::decay_t<ValueType> must meet the requirements of CopyConstructible. |
||
A reference to the new contained object.
Throws any exception thrown by T's constructor. If an exception is thrown, the previously contained object (if any) has been destroyed, and *this does not contain a value.
constructs an any object (public member function) |
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| destroys contained object (public member function) |
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