std::any::any
constexpr any() noexcept; | (1) | (since C++17) |
any( const any& other ); | (2) | (since C++17) |
any( any&& other ) noexcept; | (3) | (since C++17) |
template< class ValueType > any( ValueType&& value ); | (4) | (since C++17) |
template< class ValueType, class... Args > explicit any( std::in_place_type_t<ValueType>, Args&&... args ); | (5) | (since C++17) |
template< class ValueType, class U, class... Args >
explicit any( std::in_place_type_t<ValueType>, std::initializer_list<U> il,
Args&&... args );
| (6) | (since C++17) |
Constructs a new any object.
1) Constructs an empty object.
2-3) Copies (2) or moves (3) content of
other into a new instance, so that any content is equivalent in both type and value to those of other prior to the constructor call, or empty if other is empty. Formally,
2) If
other is empty, the constructed object is empty. Otherwise, equivalent to any(std::in_place_type<T>, std::any_cast<const T&>(other)), where T is the type of the object contained in other.
3) If
other is empty, the constructed object is empty. Otherwise, the constructed object contains either the object contained in other, or an object of the same type constructed from the object contained in other, considering that object as an rvalue.
4) Constructs an object with initial content an object of type
std::decay_t<ValueType>, direct-initialized from std::forward<ValueType>(value). If std::is_copy_constructible<std::decay_t<ValueType>>::value is false, the program is ill-formed. This overload only participates in overload resolution if std::decay_t<ValueType> is not the same type as any nor a specialization of std::in_place_type_t, and std::is_copy_constructible_v<std::decay_t<ValueType>> is true.
5) Constructs an object with initial content an object of type
std::decay_t<ValueType>, direct-non-list-initialized from std::forward<Args>(args).... 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.
6) Constructs an object with initial content an object of type
std::decay_t<ValueType>, direct-non-list-initialized from il, std::forward<Args>(args).... 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. Template parameters
| ValueType | - | contained value type |
| Type requirements | ||
-std::decay_t<ValueType> must meet the requirements of CopyConstructible. |
||
Parameters
| other | - | another any object to copy or move from |
| value | - | value to initialize the contained value with |
| il, args | - | arguments to be passed to the constructor of the contained object |
Exceptions
2,4,5,6) Throws any exception thrown by the constructor of the contained type.
Notes
Because the default constructor is constexpr, static std::anys are initialized as part of static non-local initialization, before any dynamic non-local initialization begins. This makes it safe to use an object of type std::any in a constructor of any static object.
See also
assigns an any object (public member function) |
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