如何在某些智能指针中实现深度复制功能? [英] How to implement deep copy feature in some smart pointer?

问题描述

unique_ptr非常有用.但是，它是不可复制的.如果为它的指向性类提供病毒复制(深层复制)方法，我认为它将变得更加有用.是否有必要或有更好的实施方法?一些库中是否存在任何类似的智能指针?这是一个版本

unique_ptr is quite useful. However, it is not copyable. If virutal clone (deep copy) methods are provided for its pointed class, I think it will become more useful. Is it necessary or any better way to implement it? Any similar smart pointer exist in some library? Here is a version

template<class T>
class deep_ptr: private unique_ptr<T>
{
public:
    using unique_ptr<T>::operator *;
    using unique_ptr<T>::operator ->;
    using unique_ptr<T>::operator bool;
    using unique_ptr<T>::release;
    using unique_ptr<T>::reset;
    using unique_ptr<T>::get;

    // add (DEFAULT_CONSTRUCTOR)(MOVE_CONSTRUCTOR)(MOVE_ASSIGNMENT_METHOD) ...

    explicit deep_ptr(T* p) : unique_ptr(p) {}

    deep_ptr(deep_ptr const& r) : unique_ptr(r->clone()) {}

    deep_ptr& operator=(deep_ptrconst& r)
    { if (this != &r) reset(r->clone()); return *this; }
};

Juse觉得它非常有用，但是从没有看到类似的东西.???

Juse feel it is very useful but never see similar things. ???

推荐答案

除非我误解了您要查找的内容，否则，如果一个类具有克隆方法，那应该足以获取您要寻找的内容.

Unless I am misunderstanding what you are looking for, if a class has a clone method, that should be sufficient to get what you are looking for.

示例代码:

#include <iostream>
#include <memory>

struct A
{
   virtual ~A() {}
   virtual A* clone() = 0;
};

struct B : A
{
   B(int in = 0) : x(in) {}
   B(B const& copy) : x(copy.x) {}
   virtual ~B() {std::cout << "In B::~B()\n";}

   virtual A* clone() { return new B(*this); }
   int x;
};

int main()
{
   std::unique_ptr<A> p1(new B(10));
   std::unique_ptr<A> p2(p1->clone());
   return 0;
}

运行上述程序的输出:

In B::~B()
In B::~B()

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