我正在为学校制定计划。这是一个使用模板的链接列表。
我有一个抽象的基类：
#pragma once
#include <string>
using namespace std;
template<class T>
class LinkedListInterface
{
public:
LinkedListInterface(void){};
virtual ~LinkedListInterface(void){};
virtual void insertHead(T value) = 0;
virtual void insertTail(T value) = 0;
virtual void insertAfter(T value, T insertionNode) = 0;
virtual void remove(T value) = 0;
virtual void clear() = 0;
virtual T at(int index) = 0;
virtual int size() = 0;
};
我从中衍生出来的课程：
/* Linklist.h
*
* Created on: Oct 4, 2014
*
*/
#ifndef LINKLIST_H_
#define LINKLIST_H_
#include <iostream>
#include "LinkedListInterface.h"
template<class T>
class Linklist: public LinkedListInterface<T> {
private:
struct _node
{
T val;
Linklist *next;
};
struct _node node ;
Linklist *root = NULL;
Linklist *tail = NULL;
int _size = 0;
int finddup(T value);
public:
Linklist();
virtual ~Linklist();
void insertHead(T value);
void insertTail(T value);
void insertAfter(T value, T insertionNode);
void remove(T value);
void clear();
T at(int index);
int size();
};
#endif /* LINKLIST_H_ */
Linklist.cpp
/*
* Linklist.cpp
*
* Created on: Oct 4, 2014
*
*/
#include "Linklist.h"
template<class T>
Linklist<T>::Linklist()
{
// TODO Auto-generated constructor stub
}
template<class T>
Linklist<T>::~Linklist()
{
// TODO Auto-generated destructor stub
}
template<class T>
int Linklist<T>::finddup(T value)
{
Linklist *tmp = root;
while (tmp)
{
if (tmp->node.val == value)
{
return 1;
}
}
return 0;
}
template<class T>
void Linklist<T>::insertHead(T value)
{
Linklist *tmp = root;
if (finddup(value))
{
return;
}
else
{
if (!root)
{
root = new Linklist<T>();
root->val = value;
root->next = NULL;
tail = root;
_size++;
}
else
{
Linklist *newr = new Linklist<T>();
newr->node.val = value;
newr->node.next = root;
root = &newr;
_size++;
}
}
}
template<class T>
void Linklist<T>::insertTail(T value)
{
Linklist *tmp = root;
if (finddup(value))
{
return;
}
else
{
if (!tail)
{
tail = new Linklist<T>();
tail->val = value;
tail->next = NULL;
root = tail;
_size++;
}
else
{
Linklist *newr = new Linklist<T>();
newr->node.val = value;
newr->node.next = NULL;
tail->node.next = &newr;
tail = &newr;
_size++;
}
}
}
template<class T>
void Linklist<T>::insertAfter(T value, T insertionNode)
{
if (finddup(value))
{
return;
}
else
{
Linklist *tmp = root;
while (tmp)
{
if (tmp->node.val == insertionNode)
{
Linklist *newr = new Linklist<T>();
newr->node.val = value;
newr->node.next = tmp->node.next;
tmp->node.next = &newr;
_size++;
break;
}
else
tmp = tmp->node.next;
}
}
}
template<class T>
void Linklist<T>::remove(T value)
{
Linklist *prev = NULL, *active = NULL;
if (!root)
std::cout << "List is empty" << std::endl;
else
{
if (root && root->node.val == value)
{
Linklist *t = root;
root = t->node.next;
delete t;
_size--;
}
}
prev = root;
active = root->node.next;
while (active)
{
if (active->node.val == value)
{
prev->node.next = active->node.next;
delete active;
_size--;
active = prev->node.next;
}
else
{
prev = active;
active = active->node.next;
}
}
}
template<class T>
void Linklist<T>::clear()
{
Linklist *t = root;
while (t)
{
t = root->node.next;
delete root;
root = t;
}
root = NULL;
tail = NULL;
_size = 0;
}
template<class T>
T Linklist<T>::at(int index)
{
Linklist *t = root;
if (index < _size)
{
for (int i = 0; i < _size; i++)
{
t = t->node.next;
}
}
else
{
t = NULL;
}
return (t);
}
template<class T>
int Linklist<T>::size()
{
return (_size);
}
那些似乎没问题。问题是当我尝试在提供并修改的工厂类中创建Linklist对象时。
#include "Factory.h"
#include "Linklist.h"
//You may add #include statements here
/*
You will MODIFY THIS DOCUMENT.
*/
/*
getLinkedListInt() and
Creates and returns an object whose class extends LinkedListInterface.
This should be an object of a class you have created.
Example: If you made a class called "LinkedList", you might say, "return new LinkedList<int>();".
*/
LinkedListInterface<int> * Factory::getLinkedListInt()
{
return new Linklist<int>();
}
/*
getLinkedListString() and
Creates and returns an object whose class extends LinkedListInterface.
This should be an object of a class you have created.
Example: If you made a class called "LinkedList", you might say, "return new LinkedList<string>();".
*/
LinkedListInterface<string>* Factory::getLinkedListString()
{
return new Linklist<string>();
}
我被告知：
undefined reference to `Linklist<int>::Linklist()'
undefined reference to `Linklist<string>::Linklist()'
编译时我不太了解模板，不知道我搞砸了什么。
有人有任何建议吗？
由于
答案 0 :(得分：0)
不开始工作：
的main.cpp
#include "Source.h"
int main() {
Linklist<int> obj;
}
Source.h
#pragma once
template <class T>
class Linklist {
public:
Linklist();
};
Source.cpp
#include "Source.h"
template <class T>
Linklist<T>::Linklist() {}
输出：
错误LNK2019：未解析的外部符号“public：__ cdecl Linklist :: Linklist（void）”
这是因为模板的实例化方式。
在您的特定情况下，您可以显式实例化int和string类型，也可以更改设计，以便在头文件中包含声明和定义。
了解更多信息：Why can templates only be implemented in the header file?