std::any::operator=

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Utilities library

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(C++26)

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three_way_comparablethree_way_comparable_with

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(C++20)

common_comparison_category

(C++20)

compare_three_way_result

(C++20)

(C++20)

(C++20)

(C++20)

(C++20)

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(C++20)

compare_weak_order_fallback

(C++20)

compare_partial_order_fallback

(C++20)

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(C++20)(C++20)(C++20)

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(C++20)(C++20)(C++20)

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rel_ops::operator!=rel_ops::operator>

rel_ops::operator<=rel_ops::operator>=

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cmp_equalcmp_lesscmp_less_than

(C++20)(C++20)(C++20)

cmp_not_equalcmp_greatercmp_greater_than

(C++20)(C++20)(C++20)

in_range

(C++20)

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swap
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to_underlying (C++23)

forward (C++11)
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as_const (C++17)

Common vocabulary types

pair
tuple (C++11)
optional (C++17)
any (C++17)
variant (C++17)

tuple_size (C++11)
tuple_element (C++11)
apply (C++17)
make_from_tuple (C++17)
expected (C++23)

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std::any

Member functions
any::any
any::~any
any::operator=
Modifiers
any::emplace
any::reset
any::swap
Observers
any::has_value
any::type
Non-member functions
swap(std::any)
any_cast
make_any
Helper classes
bad_any_cast

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any& operator=(const any& rhs);	(1)	(since C++17)
any& operator=( any&& rhs)noexcept;	(2)	(since C++17)
template<typename ValueType> any& operator=( ValueType&& rhs);	(3)	(since C++17)

Assigns contents to the contained value.

1) Assigns by copying the state ofrhs, as if bystd::any(rhs).swap(*this).

2) Assigns by moving the state ofrhs, as if bystd::any(std::move(rhs)).swap(*this).rhs is left in a valid but unspecified state after the assignment.

3) Assigns the type and value ofrhs, as if bystd::any(std::forward<ValueType>(rhs)).swap(*this). This overload participates in overload resolution only ifstd::decay_t<ValueType> is not the same type asstd::any andstd::is_copy_constructible_v<std::decay_t<ValueType>> istrue.

[edit]Template parameters

ValueType	-	contained value type
Type requirements
- `std::decay_t<ValueType>` must meet the requirements ofCopyConstructible.

[edit]Parameters

rhs

object whose contained value to assign

[edit]Return value

*this

[edit]Exceptions

1,3) Throwsstd::bad_alloc or any exception thrown by the constructor of the contained type.If an exception is thrown for any reason, these functions have no effect (strong exception safety guarantee).

[edit]Example

Run this code

#include <any>#include <cassert>#include <iomanip>#include <iostream>#include <string>#include <typeinfo> int main(){usingnamespace std::string_literals;std::string cat{"cat"}; std::any a1{42};std::any a2{cat};assert(a1.type()==typeid(int));assert(a2.type()==typeid(std::string));     a1= a2;// overload (1)assert(a1.type()==typeid(std::string));assert(a2.type()==typeid(std::string));assert(std::any_cast<std::string&>(a1)== cat);assert(std::any_cast<std::string&>(a2)== cat);     a1=96;// overload (3)    a2="dog"s;// overload (3)    a1= std::move(a2);// overload (2)assert(a1.type()==typeid(std::string));assert(std::any_cast<std::string&>(a1)=="dog");// The state of a2 is valid but unspecified. In fact,// it is void in gcc/clang and std::string in msvc.std::cout<<"a2.type(): "<<std::quoted(a2.type().name())<<'\n';     a1= std::move(cat);// overload (3)assert(*std::any_cast<std::string>(&a1)=="cat");// The state of cat is valid but indeterminate:std::cout<<"cat: "<<std::quoted(cat)<<'\n';}