如何正确实现“三大”:单链表(C++）

我正在编写一个程序，该程序包含一个用于保存购物清单的单链表。每个节点都有项目名称、数量和数量描述（例如鸡蛋的打数）。除析构函数外，程序中的所有工作项都能找到。不过我似乎找不出它有什么毛病。

驱动程序将执行到代码为return 0;的末尾，然后调用析构函数并在delete current;行上停止，并显示消息：

"项目14.exe:0xC0000005:读取位置0xFEEEFEE2时发生访问冲突，0x0FC7A9E8（msvcr120d.dll）处出现未处理的异常。".

我已经在下面发布了三大函数的实现。默认构造函数将两个指针（first、last）初始化为null，将nodeCount初始化为0。

我似乎找不出问题。有什么帮助吗？

List::List(const List& b)
{
    Node* newNodePtr = new Node;
    Node* nodeCopy = b.first;
    newNodePtr = nodeCopy;
    first = newNodePtr;
    last = newNodePtr;
    nodeCount++;
    nodeCopy = nodeCopy->getNext();
    while (last != b.last)
    {
        Node* newNode = new Node;
        newNode = nodeCopy;
        Node* currentNode = last;
        currentNode->setNext(newNode);
        last = newNode;
        nodeCount++;
        nodeCopy = nodeCopy->getNext();
    }
}
List::~List()
{
    Node* current = first;
    while (current != nullptr)
    {
        Node* _next = current->getNext();
        delete current;
        current = _next;
    }
    first = nullptr;
    last = nullptr;
}
List& List::operator=(const List& rho)
{
    Node* current = first;
    while (current != nullptr)
    {
        Node* _next = current->getNext();
        delete current;
        current = _next;
    }
    first = nullptr;
    last = nullptr;
    Node* newNodePtr = new Node;
    Node* nodeCopy = rho.first;
    newNodePtr = nodeCopy;
    first = newNodePtr;
    last = newNodePtr;
    nodeCount++;
    nodeCopy = nodeCopy->getNext();
    while (last != rho.last)
    {
        Node* newNode = new Node;
        newNode = nodeCopy;
        Node* currentNode = last;
        currentNode->setNext(newNode);
        last = newNode;
        nodeCount++;
        nodeCopy = nodeCopy->getNext();
    }
    return *this;
}

编辑：我还添加了我的push_back函数，如下所示：

void List::push_back(Node* newNode)
{
if (first == nullptr)
{
    first = newNode;
    last = newNode;
}
else
{
    Node* currentNode = last;
    currentNode->setNext(newNode);
    last = newNode;
}
nodeCount++;
}

好吧，我想我已经想通了。这个代码似乎有效，它适合我的教授提供的驱动程序。下面我介绍了三大函数以及它们调用的所有其他函数：

List::List(const List& b)
{
    this->copyList(b);
}
List::~List()
{
    this->clearList();
}
List& List::operator=(const List& rho)
{
    this->clearList();
    this->copyList(rho);
    return *this;
}
void List::clearList()
{
    Node* current = first;
    while (current != nullptr)
    {
        current = pop_front();
        delete current;
        current = first;
    }
    first = nullptr;
    last = nullptr;
}
void List::copyList(const List& b)
{
    first = nullptr;
    last = nullptr;
    nodeCount = 0;
    Node *headNode = b.getFirst();
    while (headNode != nullptr)
    {
        string des = headNode->getDescription();
        string qNa = headNode->getQuantityName();
        int qNu = headNode->getQuantityNumber();
        Node* newNode = new Node(qNu, qNa, des);
        push_back(newNode);
        headNode = headNode->getNext();
    }
}
Node* List::pop_front()
{
    Node* saveFirst = first;
    first = first->getNext();
    nodeCount--;
    return saveFirst;
}
void List::push_back(Node* newNode)
{
    if (nodeCount == 0)
    {
        first = newNode;
        last = newNode;
    }
    else
    {
        Node* currentNode = last;
        currentNode->setNext(newNode);
        last = newNode;
    }
    nodeCount++;
}