std::variant::emplace
From cppreference.com
| template <class T, class... Args> T& emplace(Args&&... args); |
(1) | (since C++17) |
| template <class T, class U, class... Args> T& emplace(std::initializer_list<U> il, Args&&... args); |
(2) | (since C++17) |
| template <size_t I, class... Args> std::variant_alternative_t<I, variant>& emplace(Args&&... args); |
(3) | (since C++17) |
| template <size_t I, class U, class... Args> std::variant_alternative_t<I, variant>& emplace(std::initializer_list<U> il, Args&&... args); |
(4) | (since C++17) |
Creates a new value in-place, in an existing variant object
1) Equivalent to emplace<I>(std::forward<Args>(args)...), where
I is the zero-based index of T in Types.... This overload only participates in overload resolution if std::is_constructible_v<T, Args...> is true, and T occurs exactly once in Types...2) Equivalent to emplace<I>(il, std::forward<Args>(args)...), where
I is the zero-based index of T in Types.... This overload only participates in overload resolution if std::is_constructible_v<T, std::initializer_list<U>&, Args...> is true, and T occurs exactly once in Types...3) First, destroys the currently contained value (if any). Then direct-initializes the contained value as if constructing a value of type
T_I with the arguments std::forward<Args>(args).... If an exception is thrown, *this may become valueless_by_exception.
This overload only participates in overload resolution if std::is_constructible_v<T_I, Args...> is true. The behavior is undefined if I is not less than sizeof...(Types).4) First, destroys the currently contained value (if any). Then direct-initializes the contained value as if constructing a value of type
T_I with the arguments il, std::forward<Args>(args).... If an exception is thrown, *this may become valueless_by_exception.
This overload only participates in overload resolution if std::is_constructible_v<T_I, initializer_list<U>&, Args...> is true. The behavior is undefined if I is not less than sizeof...(Types).Contents |
[edit] Parameters
| args | - | constructor arguments to use when constructing the new value |
| il | - | initializer_list argument to use when constructing the new value |
[edit] Return value
A reference to the new contained value.
[edit] Exceptions
1-4) Any exception thrown during the initialization of the contained value.
[edit] Example
| This section is incomplete Reason: no example |
[edit] See also
| assigns a variant (public member function) |