std::optional::emplace
From cppreference.com
| template< class... Args >
void emplace( Args&&... args ); |
(since C++17) | |
| template< class U, class... Args >
void emplace( std::initializer_list<U> ilist, Args&&... args ); |
(since C++17) | |
Constructs the contained value in-place. If *this already contains a value before the call, the contained value is destroyed by calling its destructor.
1) Initializes the contained value by direct-initializing (but not direct-list-initializing) with std::forward<Args>(args)... as parameters.
2) Initializes the contained value by calling its constructor with ilist, std::forward<Args>(args)... as parameters. This overload only participates in overload resolution if std::is_constructible<T, std::initializer_list<U>&, Args&&...>::value is true.
Contents |
[edit] Parameters
| args... | - | the arguments to pass to the constructor |
| ilist | - | the initializer list to pass to the constructor |
| Type requirements | ||
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T must be constructible from Args...
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T must be constructible from std::initializer_list and Args...
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[edit] Return value
(none)
[edit] Exceptions
Any exception thrown by the selected constructor of T. If an exception is thrown, *this does not contain a value after this call (the previously contained value, if any, had been destroyed).
[edit] See also
| assigns contents (public member function) |