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std::any:: reset

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< cpp ‎ | utility ‎ | any

Utilities library

Language support

Type support (basic types, RTTI)

Library feature-test macros (C++20)

Program utilities

Variadic functions

initializer_list

(C++11)

is_constant_evaluated

(C++20)

is_within_lifetime

(C++26)

source_location

(C++20)

Coroutine support (C++20)

Contract support (C++26)

Three-way comparison

three_way_comparable three_way_comparable_with

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

strong_ordering

(C++20)

(C++20)

partial_ordering

(C++20)

common_comparison_category

(C++20)

compare_three_way_result

(C++20)

compare_three_way

(C++20)

(C++20)

(C++20)

(C++20)

compare_strong_order_fallback

(C++20)

compare_weak_order_fallback

(C++20)

compare_partial_order_fallback

(C++20)

is_eq is_lt is_lteq

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

is_neq is_gt is_gteq

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

General utilities

Function objects
Bit manipulation (C++20)
C-style bit manipulation (C++26)
bitset
hash (C++11)

Relational operators (deprecated in C++20)

rel_ops::operator!= rel_ops::operator>

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

Integer comparison functions

cmp_equal cmp_less cmp_less_than

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

cmp_not_equal cmp_greater cmp_greater_than

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

(C++20)

Swap and type operations

swap
ranges::swap (C++20)
exchange (C++14)
declval (C++11)
to_underlying (C++23)

forward (C++11)
forward_like (C++23)
move (C++11)
move_if_noexcept (C++11)
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)

void reset ( ) noexcept ;		(自 C++17 起)

如果 * this 包含值，则销毁所含值。

* this 在此调用后将不包含任何值。

目录

参数

(无)

返回值

(无)

示例

运行此代码

#include <any>
#include <cassert>
int main()
{
    std::any a{42};
    assert(a.has_value());
    a.reset();
    assert(not a.has_value());
}

参见

检查对象是否持有值
(公开成员函数)