c++ - 如何在*成员被销毁后*在析构函数中执行一些代码

Question

我有一个“经理”类，它必须在成员被销毁后做一些清理工作:

class Manager
{
    Member a, b;

    ~Manager()
    {
        // this code will be executed BEFORE the a and b destructors
        important_cleanup();
    }
};

这里的问题是 important_cleanup() 使我的变量 a 和 b 无效，因此它们的析构函数失败。

是否有解决该问题的好方法？

PS 我知道我可以定义某种 clenup 成员，并使其成为 Manager 的第一个创建成员，但这看起来很丑陋并且使事情变得井井有条-依赖...

Answer 1

依赖销毁顺序确实不容易出错，假设您还发表了一条评论，说明成员顺序对特定成员很重要。将其放入语言中是有原因的，因此使用起来完全没问题。

就是说，如果您不放心依赖它，destructors of members are called before those of the base classes,所以你可以使用一个基类来做到这一点:

class ManagerCleanup {
public:
    ~ManagerCleanup() {
        important_cleanup();
    }

private:
    some_native_resource resource;
};

// Might as well inherit privately
class Manager : private ManagerCleanup
{
    Member a, b;
};

请注意，如果您包装资源，它会更加地道:

// Note: this could probably be a std::unique_ptr. std::unique_ptr can
// manage arbitrary resources, not just pointers.
class ItemRequiringCleanup {
public:
    // Ensure you implement/disable copy/move operations appropriately

    ~ItemRequiringCleanup() {
        important_cleanup();
    }

private:
    some_native_resource resource;
};

class ManagerCleanup {
private: // or protected:
    ItemRequiringCleanup resource;
};

// Might as well inherit privately
class Manager : private ManagerCleanup
{
    Member a, b;
};