Question

我正在尝试为类项目创建一个队列数组。我已经为FIFO队列编写了规范文件和实现文件。但是，当我写：

QueType<movieType> fifoQueue[6];

我收到此错误消息：

错误LNK2019：未解析的外部符号“public：__thiscall QueType :: QueType（void）”（?? 0？$ QueType @ VmovieType @@@@ QAE @ XZ）在函数_main`中引用

为了能够创建队列数组，我必须添加什么。另外，我不能使用STL队列。

这是主文件：

#include "movieType.h" 
#include <iostream>
#include <fstream>
#include "QueType.h"

using namespace std;

int main()
{
movieType movie[9];
ifstream inFile("movie1.txt");

    //I get the error here
    QueType<movieType> fifoQueue[6];

    return 0;
}

这是规范文件：

//definition of NodeType
template <class ItemType>
struct NodeType
{
ItemType info; // store data
NodeType* next; // sotre location of data
};

//exception class used when queue is full
class FullQueue
{};

//Exception class used when queue is empty
class EmptyQueue
{};

//templated queue class
template<class ItemType>
class QueType
{
public:
    QueType();
    //Function: class constructor
    //Precondition: none
    //Postcondition: it initializes the pointers, front and rear to null

    ~QueType();
    //Function:class destructor
    //Precondition: queue has been initialized
    //Postcondition: deallocate allocated memory

    void MakeEmpty();
    //Function: determines whether the queue is empty
    //Precondition: queue has been initialized
    //Postcondition:queue is empty

    bool IsEmpty() const;
    //Function:determines whether the queue is empty
    //Precondition:queue has been initialized
    //Postcondition:Function value = (queue is empty)

    bool IsFull() const;
    //Function:determines whether the queue is full
    //Precondition:queue has been initialized
    //Postcondition:Function value = (queue is full)

    void Enqueue(ItemType newItem);
    //Function:Adds newItem to the rear of the queue
    //Precondition:queue has been initialized
    //Postcondition:if (queue is full), FullQueue exception is thrown,
    //else newItem is at rear of queue

    void Dequeue(ItemType& item);
    //Function:removes front item from the queue and returns it in item
    //Precondition:queue has been initialized
    //Postcondition:if (queue is empty), EmptyQueue exception is thrown
    //and item is undefines, else front element has been removed from
    //queue and item is a copy of removed element

private:
    NodeType<ItemType>* front; //pointer points to the front to the queue
    NodeType<ItemType>* rear; // pointer points to the rear of the queue
};

和规范文件：

#include "QueType.h"//gives access to QueType class
#include <cstddef> //for NULL
#include <new> // for bad_alloc

template<class ItemType>
QueType<ItemType>::QueType()
{
front = NULL;
rear = NULL;
}

template <class ItemType>
QueType<ItemType>::~QueType()
{
MakeEmpty();
}

template <class ItemType>
void QueType<ItemType>::MakeEmpty()
{
NodeType<ItemType>* tempPtr;//temporary pointer

while(front != NULL)
{
    tempPtr=front;
    front = front->next;
    delete tempPtr;
}
rear = NULL;
}

template <class ItemType>
bool QueType<ItemType>::IsEmpty() const
{
return (front == NULL);
}

template <class ItemType>
bool QueType<ItemType>::IsFull() const
{
NodeType<ItemType>* location;
try
{
    location = new NodeType<ItemType>
    delete location;
    return false;
}
catch(std::bad_alloc exception)
{
    return true;
}
}

template <class ItemType>
void QueType<ItemType>::Enqueue(ItemType newItem)
{
if (IsFull())
        throw FullQueue();
else
{
    NodeType<ItemType>* newNode;
    newNode = new NodeType<ItemType>;
    newNode ->info=newItem;
    newNode->next=NULL;
    if(rear== NULL)
            front= newNode;
    else
            rear->next=newNode;
    rear=newNode;
}
}

Answer 1

您需要实现“规范文件”中声明的函数。

此特定错误消息只是抱怨QueType构造函数缺少实现（因为这是您在QueType中使用的main的唯一功能），但是只要如果您开始使用任何其他函数，您将收到类似的链接器错误。

在这种情况下，因为您的类是模板化的，所以您需要将定义移动到头文件中，以便让编译器在创建特化时访问它们。

有关详细信息，请参阅this question。

如何创建队列数组？

1 个答案: