std::expected<T,E>::emplace
| Primary template | ||
template< class... Args > constexpr T& emplace( Args&&... args ) noexcept; | (1) | (since C++23) |
template< class U, class... Args > constexpr T& emplace( std::initializer_list<U> il, Args&&... args ) noexcept; | (2) | (since C++23) |
| void partial specialization | ||
constexpr void emplace() noexcept; | (3) | (since C++23) |
Constructs an expected value in-place. After the call, has_value() returns true.
1) Destroys the contained value, then direct-initializes the expected value contained in
*this with std::forward<Args>(args)....
This overload participates in overload resolution only if
std::is_nothrow_constructible_v<T, Args...> is true.
2) Destroys the contained value, then direct-initializes the expected value contained in
*this with il and std::forward<Args>(args)....
This overload participates in overload resolution only if
std::is_nothrow_constructible_v<T, std::initializer_list<U>&, Args...> is true.
3) If
*this contains an unexpected value, destroys that value.Parameters
| args | - | the arguments to pass to the constructor |
| il | - | the initializer list to pass to the constructor |
Return value
1)
*std::construct_at(std::addressof(val),std::forward<Args>(args)...)
2)
*std::construct_at(std::addressof(val),il,std::forward<Args>(args)...)
Notes
If the construction of T is potentially-throwing, operator= can be used instead.
Example
See also
| assigns contents (public member function) |
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