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std::optional::operator*

可选：：操作符->，std：：可选：：Operator%2A

constexpr const T* operator->() const;(1)(since C++17)
constexpr T* operator->((1)(since C++17)
constexpr const T& operator*() const&;(2)(since C++17)
constexpr T& operator*() &;(2)(since C++17)
constexpr const T&& operator*() const&&;(2)(since C++17)
constexpr T&& operator*() &&;(2)(since C++17)

访问包含的值。

1%29返回指向包含的值的指针。

2%29返回对包含的值的引用。

如果*this不包含值。

参数

%280%29

返回值

指针或对包含的值的引用。

例外

%280%29

注记

此运算符不检查可选选项是否包含值。如果需要检查访问，value()或value_or()可能会被使用。

例

二次

#include <optional>
#include <iostream>
#include <string>
int main()
{
    using namespace std::string_literals;
 
    std::optional<int> opt1 = 1;
    std::cout << *opt1 << '\n';
 
    std::optional<std::string> opt2 = "abc"s;
    std::cout << opt2->size() << '\n';
}

二次

产出：

二次

1
3

二次

另见

valuereturns the contained value (public member function)
value_orreturns the contained value if available, another value otherwise (public member function)

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