Question

我应该实现堆栈的功能，我得到了main.cpp文件，然后留下来写其他文件，即StackofNodes.hpp＆amp; 。H。这些依赖于另外两个文件Node.hpp＆amp; 。H。当我尝试构建程序时，我得到了给我的main.cpp文件的错误。这是：

obj/Debug/main.o||In function `main':|
|6|undefined reference to `StackOfNodees<int>::StackOfNodees()'|
|12|undefined reference to `StackOfNodees<int>::push(int)'|
|17|undefined reference to `StackOfNodees<int>::size() const'|
|24|undefined reference to `StackOfNodees<int>::pop()'|

的main.cpp

   #include <iostream> //std::cout std::cin
    #include "StackOfNodees.h" //StackOfNodes

    int main()
    {
        StackOfNodees<int> myStack; //Create an empty stack
        int sizeOfStack;    //int we'll use later to store the size of the stack

        //push some numbers onto the stack
        for(int i = 1; i <= 10; i++)
        {
            myStack.push( i * 5 );
        }


        //Store the size of the stack before popping anything
        sizeOfStack = myStack.size();

        std::cout << "There are " << sizeOfStack << " items on the stack" << std::endl;

        //Think about why we don't use i<myStack.size()
        for(int i = 0; i < sizeOfStack; i++)
        {
            std::cout << "Popping the top: " << myStack.pop() << std::endl;
        }

            /* while(!myStack.isEmpty()) is another valid way to pop all the contents of the stack */

    }

StackOfNodees.hpp

#ifndef STACKOFNODEES_HPP_INCLUDED
#define STACKOFNODEES_HPP_INCLUDED

StackOfNodees::StackOfNodees()
{
    m_top=nullptr;
    m_size=0;
}

bool StackOfNodees::isEmpty() const
{
    if (m_size==0)
    {
        return true;
    }
    return false;
}

int StackOfNodees::size() const
{
    return m_size;
}

void StackOfNodees::push(int value)
{
    Node* Node1 = new Node;
    Node1 -> m_previous = m_top;
    m_top=Node1;
    Node1 -> m_value = value;
    ++m_size;
}

int StackOfNodees::pop()
{
    // initialize
    int returnval = 0;

    if (!isEmpty())
    {
        // fetch the value from the top one
        returnval = m_top -> m_value;

        Node* temp = m_top;

        //move m_top down to previous box.
        m_top = m_top -> m_previous;

        //delete the popped one
        delete temp;

        m_size--;
    }
    else
    {
        // you may want to throw an exception here for popping a empty stack
    }

    return returnval;
}




#endif // STACKOFNODEES_HPP_INCLUDED

Node.h

#ifndef NODE_H_INCLUDED
#define NODE_H_INCLUDED

template<typename T>
Node<T>::Node()
{
    Node.setPrevious(nullptr);
    Node.setValue();
}

//initiation of getters
    template<typename T>
    T Node::getValue()
    {
        return m_value;
    }//end getValue

    template<typename int>
    int Node::getPrevious()
    {
        return m_previous;
    }//end getPrevious

//initiation of setters
    template<typename void>
    void Node::setValue(T value)
    {
        m_value =  value;
    }//end setValue

    template<typename void>
    void Node::setPrevious(Node<T>* previous)
    {
        Node<T>* previous = m_previous;
    }//end setPrevious

StackOfNodees.h

#ifndef STACKOFNODEES_H_INCLUDED
#define STACKOFNODEES_H_INCLUDED
#include "Node.h"

template<typename T>
class StackOfNodees
{
private:
    Node<T>* m_top;
    int m_size;

public:
    StackOfNodees();
    bool isEmpty() const;
    int size() const;
    void push(T value);
    T pop();
};

#endif // STACKOFNODEES_H_INCLUDED

非常感谢任何帮助。谢谢！

Answer 1

您没有定义模板类StackOfNodees的方法。你需要

template<typename T>
StackOfNodees<T>::StackOfNodees()
{
    m_top=nullptr;
    m_size=0;
}

而不是

StackOfNodees::StackOfNodees()
{
    m_top=nullptr;
    m_size=0;
}

更改所有定义并将其从.hpp移动到StackOfNodees.h文件中。您不需要额外的.hpp文件。

示例：

// File a.h
template<typename T>
class A
{
public:
    A();
    // the rest of the class ....
};

template<typename T>
A<T>::A()
{
    // ...
}

文件app.cpp

#include "a.h"
void main()
{
    A<int> a;
...
}

额外的.hpp文件会降低代码的可读性 ，因为它会破坏阅读流程。如果您仍然需要以这种方式拆分代码，那么您需要将.hpp包含在.h文件中，并在.h文件底部包含#include "StackOfNodes.hpp"指令（这是一种非常规的方法）。

Answer 2

在编写模板类时，必须在声明本身所在的同一文件中提供模板类的定义，以便编译器在编译时可以实例化实际的类。

在这种特定情况下，将StackOfNodees.hpp特定的一个更改为常规类型StackOfNodees.h之后，将int中的定义放回文件T中的模板类声明中。 This是一个关于模板类格式的简单教程。

未定义的引用一般错误

2 个答案: