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std::shared_ptr<T>:: unique

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bool unique ( ) const noexcept ;
(C++17 起已弃用)
(C++20 起移除)

检查 * this 是否为当前管理对象的唯一 shared_ptr 实例，即是否满足 use_count ( ) == 1 。

目录

参数

(无)

返回值

当 * this 是唯一管理当前对象的 shared_ptr 实例时返回 true ，否则返回 false 。

注释

此函数在C++17中已弃用并在C++20中移除，因为 use_count ( ) == 1 在多线程环境中无意义（参见 use_count 中的 说明 ）。

示例

运行此代码 
#include <iostream> 
#include <memory> 
int main() 
{ 
    auto sp1 = std::make_shared<int>(5);
    std::cout << std::boolalpha;
    std::cout << "sp1.unique() == " << sp1.unique() << '\n'; 
    std::shared_ptr<int> sp2 = sp1; 
    std::cout << "sp1.unique() == " << sp1.unique() << '\n'; 
}

输出： 

sp1.unique() == true
sp1.unique() == false

参见

返回引用同一被管理对象的 shared_ptr 对象数量
(公开成员函数)