C++对象 - 私有int返回奇怪的值

Question

我一直在教自己C++,并开始创建一个列表组织器来处理指针的概念.

我已经定义了一个名为List的类,它有三个属性:

int itemTotal;
Item* firstItem;
Item* lastItem;

构造函数将其值设置为:

itemTotal = 0;
firstItem = NULL;
lastItem = NULL;

我已经构建了一个函数来返回itemTotal的值:

int List::getItemTotal()
{
    return itemTotal;
}

在我的驱动程序中构建对象之后,itemTotal立即开始表现得很有趣并返回非常大的数字(每次都是-858993460),即使在List上没有完成任何工作,并且在程序中没有发生任何事情.我在构造函数中添加了一个cout,只是为了看看那里发生了什么,并且它回显了0值,但是一旦构造函数完成,值就会立即改变.

我一直试图用我的书来解决它并玩弄它,但我似乎无法解决这个问题,所以我想我会转向有经验的人.主要在以下:

int main()
{
    List grocery;
    cout << "itemTotal is now: " << grocery.getItemTotal() << endl; // Returns wrong value...


    system("Pause");
    return 0;
}

输出看起来像:

grocery List is built!
itemTotal inside of the constructor is 0!
itemTotal is now: -858993460

有任何想法吗？= /

编辑:每个请求,整个类(抱歉格式是丑陋的,我不想重新做这一切):

class List
{
public:
// Constructor
// Purpose: Builds object.
// Returns: Nothing.
// Pre-Conditions: None.
// Post-Conditions: Initializes null.
List();

// push_back function
// Purpose: Adds Item to end of List.
// Returns: None.
// Pre-Conditions: Must pass a declared Item object.
// Post-Conditions: None.
void push_back(Node*);

// push_front function
// Purpose: Adds Item to beginning of List.
// Returns: None.
// Pre-Conditions: Must pass a declared Item object.
// Post-Conditions: None.
void push_front(Node*);

// pop_back function
// Purpose: Removes last Item from List. Item is NOT deleted.
// Returns: Pointer to removed Item.
// Pre-Conditions: None.
// Post-Conditions: None.
Node* pop_back();

// pop_front function
// Purpose: Removes first Item from List. Item is NOT deleted.
// Returns: Pointer to removed Item.
// Pre-Conditions: None.
// Post-Conditions: None.
Node* pop_front();

// getFirst function
// Purpose: Returns pointer to first Item in List.
// Returns: Pointer.
// Pre-Conditions: List must have a Item object.
// Post-Conditions: None.
Node* getFirst();

// getItemTotal function
// Purpose: Returns the itemTotal
// Returns: Int
// Pre-Conditions: None.
// Post-Conditions: None.
int getItemTotal();
private:
Item* firstitem;
Item* lastitem;
int itemTotal;

}

和构造函数:

List::List()
{
Item* firstNode = NULL;
Item* lastNode = NULL;
int itemTotal = 0;
cout << "item total should start at 0, it is " << nodeTotal << " inside of the constructor." << endl;
}

Answer 1

HAAA!您正在构造函数中初始化局部变量而不是成员!而不是int itemTotal = 0;写this->itemTotal = 0;或只是itemTotal = 0甚至使用像这样的构造函数初始化列表

List::list()
   :itemTotal(0),
    firstNode(NULL),
    lastNode(NULL)   
{
   cout << "List ctor Called"
}