C++智能指针与容器结合使用方法

iv>

答案：C++智能指针与容器结合使用可实现安全的内存管理。通过std::unique_ptr实现独占所有权，确保容器销毁时自动释放资源；用std::shared_ptr实现共享所有权，配合引用计数避免内存泄漏。两者均遵循RAII原则，提升异常安全性和代码清晰度。使用时需注意unique_ptr的移动语义、shared_ptr的循环引用及性能开销，推荐emplace_back和make_unique/make_shared优化构造。

<p><img src="https://img.php.cn/upload/article/000/969/633/175816446275250.png" alt="C++智能指针与容器结合使用方法">p> <p>C++智能指针与容器的结合使用，核心在于理解它们各自的生命周期管理机制，并选择合适的智能指针来适配容器的存储语义。说白了，就是如何让容器安全地管理那些我们通过iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>newpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>出来的动态对象，避免内存泄漏，同时又能享受C++标准库容器带来的便利。这其中涉及到的不仅仅是语法糖，更是对资源管理哲学的一种深刻实践。p>

解决方案

<p>当我们需要在C++容器中存放动态分配的对象时，直接使用裸指针无疑是埋下了一颗定时炸弹。手动管理内存的复杂性，尤其是在异常发生时，极易导致内存泄漏。智能指针的引入，就是为了解决这个痛点，它利用RAII（Resource Acquisition Is Initialization）原则，将资源的生命周期与对象的生命周期绑定，从而实现自动化的内存管理。p> <p>具体到实践中，我们通常会根据对象的拥有权语义来选择iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>或iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::shared_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>。p> <p>1. 独占所有权场景：使用 iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>p> <p>pan>立即学习pan>“ps://pan.quark.cn/s/6e7abc4abb9f" style="text-decoration: underline !important; color: blue; font-weight: bolder;" rel="nofollow" target="_blank">C++免费学习笔记（深入）”；p> <p>如果容器中的每个元素都应该独占它所指向的对象，也就是说，当元素从容器中移除或容器本身被销毁时，它所管理的对象也应该被销毁，那么iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>是最佳选择。p>iv style="position:relative; padding:0px; margin:0px;"><pre>#include <vector> #include <memory> #include <iostream> class MyObject { public: int id; MyObject(int i) : id(i) { std::cout << "MyObject " << id << " created." << std::endl; } ~MyObject() { std::cout << "MyObject " << id << " destroyed." << std::endl; } void do_something() { std::cout << "MyObject " << id << " doing something." << std::endl; } }; // 示例：std::vector 存储 std::unique_ptr std::vector<std::unique_ptr<MyObject>> objects; // 添加元素 // 方式一：直接创建并移动 objects.push_back(std::make_unique<MyObject>(1)); // 方式二：使用 emplace_back，可能更高效，避免临时对象 objects.emplace_back(std::make_unique<MyObject>(2)); // 方式三：从现有 unique_ptr 移动 auto temp_ptr = std::make_unique<MyObject>(3); objects.push_back(std::move(temp_ptr)); // temp_ptr 此时为空 // 访问元素 objects[0]->do_something(); objects.back()->do_something(); // 移除元素（例如，移除最后一个） // 当 unique_ptr 被销毁时，它指向的对象也会被销毁 objects.pop_back(); // MyObject 3 destroyed. // 容器销毁时，所有 MyObject 都会被销毁 // (示例中省略了 main 函数的结束，但原理一致)pre>iv>iv>iv><p>这里要强调的是，iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>是不可复制的，只能通过移动语义转移所有权。这意味着你不能直接将一个iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>赋值给另一个，也不能将其作为函数参数按值传递（除非你打算转移所有权）。在容器中，这通常意味着使用iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::movepre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>或者iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>emplace_backpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>配合iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::make_uniquepre>iv>iv>iv>iv>iv>iv>iv>iv>iv>来构造元素。p> <p>2. 共享所有权场景：使用 iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::shared_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>p> <p>如果多个智能指针可以共同拥有一个对象，并且只有当所有拥有者都放弃所有权时，对象才会被销毁，那么iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::shared_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>就是你的选择。这在需要共享数据、实现观察者模式或缓存机制时非常有用。p>iv style="position:relative; padding:0px; margin:0px;"><pre>#include <vector> #include <memory> #include <iostream> class SharedResource { public: int value; SharedResource(int v) : value(v) { std::cout << "SharedResource " << value << " created." << std::endl; } ~SharedResource() { std::cout << "SharedResource " << value << " destroyed." << std::endl; } }; // 示例：std::vector 存储 std::shared_ptr std::vector<std::shared_ptr<SharedResource>> resources; // 创建一个共享资源 auto s_ptr1 = std::make_shared<SharedResource>(100); // 添加到容器，s_ptr1 和 resources[0] 现在共享所有权 resources.push_back(s_ptr1); // 再次添加，s_ptr1, resources[0], resources[1] 都共享所有权 resources.push_back(s_ptr1); // 也可以直接在容器中创建 resources.emplace_back(std::make_shared<SharedResource>(200)); // 此时，s_ptr1 的引用计数是 3，resources[2] 的引用计数是 1 std::cout << "s_ptr1 ref count: " << s_ptr1.use_count() << std::endl; // 输出 3 // 访问元素 resources[0]->value = 101; std::cout << "s_ptr1 value: " << s_ptr1->value << std::endl; // 输出 101 // 移除容器中的一个元素 resources.pop_back(); // SharedResource 200 destroyed. (因为它的引用计数降为 0) std::cout << "s_ptr1 ref count after pop_back: " << s_ptr1.use_count() << std::endl; // 输出 2 // s_ptr1 超出作用域或被重置时，如果它是最后一个拥有者，SharedResource 100 才会销毁。 // (示例中省略了 main 函数的结束)pre>iv>iv>iv><p>iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::shared_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>内部维护了一个引用计数，当这个计数降到零时，它所管理的对象才会被销毁。它的拷贝是廉价的，因为只是复制了指针和增加了引用计数。这使得它在多线程环境下尤其有用，但需要注意，它所管理的对象本身的线程安全性需要额外考虑。p>

为什么不直接用裸指针存放对象，智能指针能带来哪些实际好处？

<p>说实话，我刚开始学C++的时候，对智能指针这种“额外”的东西是有点抗拒的，觉得裸指针不是挺好用的吗？iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>newpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>了就iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>deletepre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>，多清晰。但真正在复杂的项目里摸爬滚打几年，尤其是在处理异常、多线程或者回调函数这些场景下，才深刻体会到裸指针带来的那种心智负担和潜在的灾难性后果。p> <p>直接用裸指针存放对象到容器里，最直接的问题就是内存泄漏。想象一下，你iv style="position:relative; padding:0px; margin:0px;"><pre>std::vector<MyObject*>pre>iv>iv>iv>里塞了一堆iv style="position:relative; padding:0px; margin:0px;"><pre>new MyObject()pre>iv>iv>iv>出来的指针，然后容器可能在某个地方iv style="position:relative; padding:0px; margin:0px;"><pre>clear()pre>iv>iv>iv>了，或者在某个函数返回时被销毁了。如果忘记对每个指针调用iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>deletepre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>，那些对象就永远地躺在内存里了，直到程序结束。这还不算完，如果容器里存储的指针指向的对象被提前iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>deletepre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>了，而容器里的指针还在，那么这个指针就成了悬空指针（dangling pointer），后续的访问将是未定义行为，程序随时可能崩溃。p> <p>智能指针，尤其是iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>和iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::shared_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>，它们的出现就是为了解决这些“人祸”。它们的核心理念是RAII（Resource Acquisition Is Initialization），简单讲就是“资源在构造时获取，在析构时释放”。p>

i> 自动化内存管理： 这是最显著的优点。你把iv style="position:relative; padding:0px; margin:0px;"><pre>std::unique_ptr<MyObject>pre>iv>iv>iv>放到容器里，当容器元素被移除、容器被销毁，或者iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>本身被重置时，它会自动调用其内部裸指针的iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>deletepre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>操作。iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>shared_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>也类似，只是它会等到最后一个引用消失时才释放。这意味着我们程序员可以把注意力更多地放在业务逻辑上，而不是繁琐且容易出错的内存管理细节上。i> i> 异常安全： 在C++中，如果一个函数在执行过程中抛出异常，那么栈上的局部变量会被正确地销毁。如果这些局部变量是智能指针，它们会负责释放所管理的内存，从而防止内存泄漏。而裸指针则不会，一旦异常抛出，后面的iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>deletepre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>语句可能就永远执行不到了。i> i> 避免悬空指针和重复释放： iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>通过移动语义确保了独占性，一个资源在任何时候都只有一个iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>拥有。iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>shared_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>则通过引用计数来确保资源只在所有拥有者都放弃后才释放，避免了重复释放的风险。虽然iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>shared_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>在某些情况下仍可能导致循环引用，但有iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::weak_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>作为解决方案。i> i> 代码意图更清晰： 当你看到iv style="position:relative; padding:0px; margin:0px;"><pre>std::vector<std::unique_ptr<MyObject>>pre>iv>iv>iv>时，你立刻就知道这个容器拥有它里面对象的所有权，并且每个对象是独一无二的。而iv style="position:relative; padding:0px; margin:0px;"><pre>std::vector<std::shared_ptr<MyObject>>pre>iv>iv>iv>则表明这些对象是共享的，可能有其他地方也持有它们的引用。这种明确的语义表达，对代码的可读性和维护性是极大的提升。i>

<p>所以，与其说智能指针是“额外”的，不如说它是现代C++中不可或缺的基石，它让我们的代码更健壮、更安全，也更易于理解。p> iv> ps://phps.yycxw.com/ai/%E6%8C%96%E9%94%99%E7%BD%91"><img src="https://img.php.cn/upload/ai_manual/000/000/000/175679997460635.png" alt="C++智能指针与容器结合使用方法"> iv> ps://phps.yycxw.com/ai/%E6%8C%96%E9%94%99%E7%BD%91">挖错网 <p>一款支持文本、图片、视频纠错和AIGC检测的内容审核校对平台。p> iv> <img src="https://phps.yycxw.com/static/images/card_xiazai.png" alt="C++智能指针与容器结合使用方法">pan>29pan> iv> iv> ps://phps.yycxw.com/ai/%E6%8C%96%E9%94%99%E7%BD%91"> pan>查看详情pan> <img src="https://phps.yycxw.com/static/images/cardxiayige-3.png" alt="C++智能指针与容器结合使用方法"> iv>

在使用iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>与容器时，有哪些需要注意的细节和常见误区？

<p>iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>和容器的结合，在我看来是处理对象独占所有权场景的最佳实践。但它毕竟是“独占”的，这就带来了一些使用上的特殊性，如果不注意，很容易踩坑。p> <p>首先，最核心的特性是不可复制性。iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>的设计理念就是“独此一份”，它不允许你通过拷贝构造或拷贝赋值来创建另一个指向相同资源的iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>。所以，像iv style="position:relative; padding:0px; margin:0px;"><pre>std::vector<std::unique_ptr<MyObject>> vec; auto p = std::make_unique<MyObject>(1); vec.push_back(p);pre>iv>iv>iv> 这样的代码是编译不过的。这是初学者最容易遇到的障碍。p> <p>要解决这个问题，你需要显式地进行所有权转移。p>

i> 使用iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::movepre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>： 当你有一个已经存在的iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>实例，想把它放入容器，或者从容器中取出来并转移所有权给另一个iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>，就必须用iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::movepre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>。例如：iv style="position:relative; padding:0px; margin:0px;"><pre>vec.push_back(std::move(p));pre>iv>iv>iv>。iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::movepre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>本质上是将一个左值强制转换为右值引用，从而允许调用iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>的移动构造函数或移动赋值运算符。执行后，原来的iv style="position:relative; padding:0px; margin:0px;"><pre>ppre>iv>iv>iv>会变成空指针。i> i> 使用iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>emplace_backpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>配合iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::make_uniquepre>iv>iv>iv>iv>iv>iv>iv>iv>iv>： 这是我个人最推荐的方式，因为它通常更高效，避免了不必要的临时对象创建和移动。iv style="position:relative; padding:0px; margin:0px;"><pre>vec.emplace_back(std::make_unique<MyObject>(4));pre>iv>iv>iv>。iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>emplace_backpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>可以直接在容器内部构造元素，而iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::make_uniquepre>iv>iv>iv>iv>iv>iv>iv>iv>iv>则负责创建对象并返回一个iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>，这个iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>会直接被移动到容器中。i>

<p>另一个常见的误区是迭代器失效与所有权转移。当你从容器中删除一个iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>元素时，该元素所管理的对象会被自动销毁。这很棒。但如果你想“取出”一个元素，而不是销毁它，你需要一些技巧。例如，要从iv style="position:relative; padding:0px; margin:0px;"><pre>std::vector<std::unique_ptr<T>>pre>iv>iv>iv>中取出第iv style="position:relative; padding:0px; margin:0px;"><pre>ipre>iv>iv>iv>个元素的所有权，你不能直接iv style="position:relative; padding:0px; margin:0px;"><pre>auto p = vec[i];pre>iv>iv>iv>（这会尝试拷贝），而是应该这样做：iv style="position:relative; padding:0px; margin:0px;"><pre>auto p = std::move(vec[i]);pre>iv>iv>iv>。之后，iv style="position:relative; padding:0px; margin:0px;"><pre>vec[i]pre>iv>iv>iv>处的iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>就变成了空指针。如果你想从容器中完全移除这个元素，同时保留所有权，你可能需要先iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::movepre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>出来，然后用iv style="position:relative; padding:0px; margin:0px;"><pre>vec.erase()pre>iv>iv>iv>或iv style="position:relative; padding:0px; margin:0px;"><pre>vec.remove()pre>iv>iv>iv>等方法删除空指针占位符。p> <p>再者，自定义删除器。iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>允许你指定一个自定义的删除器（deleter），这在管理非堆内存资源时非常有用，比如文件句柄、数据库连接等。例如，iv style="position:relative; padding:0px; margin:0px;"><pre>std::unique_ptr<FILE, decltype(&amp;fclose)> file_ptr(fopen("test.txt", "w"), &amp;fclose);pre>iv>iv>iv>。当你将这样的iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>放入容器时，容器会正确地管理这个带有自定义删除器的智能指针。p> <p>最后，要小心容器内部的排序或重新分配操作。对于iv style="position:relative; padding:0px; margin:0px;"><pre>std::vectorpre>iv>iv>iv>，当容量不足发生重新分配时，所有元素都会被移动到新的内存区域。iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>的移动语义在这里工作得很好，不会有额外开销。但如果你使用像iv style="position:relative; padding:0px; margin:0px;"><pre>std::listpre>iv>iv>iv>或iv style="position:relative; padding:0px; margin:0px;"><pre>std::mappre>iv>iv>iv>这样的容器，它们有不同的内存布局和元素管理方式，但iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>的移动语义仍然是其核心。总的来说，理解iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>unique_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>的移动语义是与容器结合使用的关键。它强制你思考所有权的转移，而不是简单的拷贝，这在编写资源安全的代码时非常有益。p>

何时选择iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;">iv style="position:relative; padding:0px; margin:0px;"><pre>std::shared_ptrpre>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>iv>与容器结合，它又有哪些性能或设计考量？