std::any::any

C++

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Language support library

Concepts library (C++20)

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Technical Specifications

Utilities library

Type support (basic types, RTTI, type traits)
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initializer_list (C++11)
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rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=
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strong_order weak_order partial_order strong_equal weak_equal	strong_ordering weak_ordering partial_ordering strong_equality weak_equality	is_eqis_neqis_ltis_lteqis_gtis_gteq
common_comparison_category
Common vocabulary types
pair tuple (C++11) apply (C++17) make_from_tuple (C++17)	optional (C++17) any (C++17) variant (C++17)
Swap, forward and move
swap
exchange (C++14)
forward (C++11)
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chars_format (C++17)
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declval (C++11)
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std::any

Member functions

any::any

any::~any

any::operator=

Modifers

any::emplace

any::reset

any::swap

Observers

any::has_value

any::type

Non-member functions

swap(std::any)

any_cast

make_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

operator=

assigns an any object (public member function)