我们本周开始在我们的CSS课程中使用模板，但是，当我们开始在实验室中深入研究它们时，我们无法理解的一些问题开始显现。
我们收到以下错误：
../Lab7PartC/DLNode.cpp:13:5: error: invalid use of template-name ‘lab7::DLNode’ without an argument list
../Lab7PartC/DLNode.cpp:20:5: error: invalid use of template-name ‘lab7::DLNode’ without an argument list
../Lab7PartC/DLNode.cpp:26:5: error: expected unqualified-id before ‘template’
../Lab7PartC/DLNode.cpp:33:5: error: invalid use of template-name ‘lab7::DLNode’ without an argument list
以下是相关的.cpp文件：
/*
* DLNode.cpp
*
* Created on: Mar 29, 2013
* Author: tony
*/
#include <cstddef>
#include "DLNode.h"
namespace lab7 {
DLNode::DLNode() {
data = 0;
next = NULL;
prev = NULL;
}
template<class T>
DLNode::DLNode(T d) {
data = d;
next = NULL;
prev = NULL;
}
template<class T>
DLNode::DLNode(T d, DLNode* n, DLNode* p) {
data = d;
next = n;
prev = p;
}
DLNode::~DLNode() {
delete next;
}
} /* namespace lab7 */
以下是相关的.h文件：
/*
* DLNode.h
*
* Created on: Mar 29, 2013
* Author: tony
*/
#ifndef DLNODE_H_
#define DLNODE_H_
namespace lab7 {
template<class T>
class DLNode {
public:
DLNode();
DLNode(T data_in);
DLNode(T data_in, DLNode* n, DLNode* p);
virtual ~DLNode();
void setNext(DLNode* n) {
next = n;
}
void setPrev(DLNode* p) {
prev = p;
}
int getData() {
return data;
}
DLNode* getNext() {
return next;
}
DLNode* getPrev() {
return prev;
}
private:
T data;
DLNode* next;
DLNode* prev;
};
} /* namespace lab7 */
#endif /* DLNODE_H_ */
我们花了一个晚上试图解决这个问题，并感谢任何有关该主题的建议。感谢。
我讨厌再次打扰你，但我修改了头文件以包含你建议的整个定义，这就是我所拥有的，这次我包括使用节点类的附加类：
/*
* DLNode.h
*
* Created on: Mar 29, 2013
* Author: tony
*/
#ifndef DLNODE_H_
#define DLNODE_H_
namespace lab7 {
template<class T>
class DLNode {
public:
DLNode<T>();
DLNode<T>(T data_in);
DLNode<T>(T data_in, DLNode* n, DLNode* p);
~DLNode<T>();
void setNext<T>(DLNode* n) {
next = n;
}
void setPrev<T>(DLNode* p) {
prev = p;
}
int getData<T>() {
return data;
}
DLNode* getNext<T>() {
return next;
}
DLNode* getPrev<T>() {
return prev;
}
private:
T data;
DLNode* next;
DLNode* prev;
};
template<class T>
DLNode<T>::DLNode() {
data = 0;
next = NULL;
prev = NULL;
}
template<class T>
DLNode<T>::DLNode(T d) {
data = d;
next = NULL;
prev = NULL;
}
template<class T>
DLNode<T>::DLNode(T d, DLNode* n, DLNode* p) {
data = d;
next = n;
prev = p;
}
template<class T>
DLNode<T>::~DLNode() {
delete next;
}
} /* namespace lab7 */
#endif /* DLNODE_H_ */
- 以及附加列表类头文件：
/*
* DLList.h
*
* Created on: Mar 29, 2013
* Author: tony
*/
#ifndef DLLIST_H_
#define DLLIST_H_
namespace lab7 {
class DLNode<T>;
template<class T>
class DLList {
public:
DLList();
virtual ~DLList();
void insert(T data);
void print();
bool search(const T key);
bool searchandremove(const T key);
void swap();
DLNode* findNode(const T key);
private:
DLNode* first;
};
template<class T>
DLList<T>::DLList() {
first = NULL;
}
template<class T>
DLList<T>::~DLList() {
delete first;
}
template<class T>
void DLList<T>::insert(T data) {
DLNode<T>* temp = first;
first = new DLNode(data, first, NULL);
if (temp == NULL)
return;
temp->setPrev(first);
}
template<class T>
void DLList<T>::print() {
DLNode* temp = first;
while (temp != NULL) {
cout << temp->getData() << " ";
temp = temp->getNext();
}
cout << endl;
}
template<class T>
bool DLList<T>::search(const T key) {
DLNode* temp = new DLNode;
bool found = false;
for (temp = first; temp != NULL; temp = temp->getNext()) {
if (temp->getData() == key)
found = true;
}
return found;
}
template<class T>
bool DLList<T>::searchandremove(const T key) {
DLNode* prev = new DLNode;
DLNode* next = new DLNode;
DLNode* toDelete = new DLNode;
toDelete = findNode(key);
if (toDelete != NULL) {
prev = toDelete->getPrev();
next = toDelete->getNext();
toDelete->setNext(NULL);
toDelete->setPrev(NULL);
if (toDelete == first) {
first = next;
next->setPrev(first);
} else {
prev->setNext(next);
if (next != NULL)
next->setPrev(prev);
}
delete toDelete;
return true;
}
return false;
}
template<class T>
DLNode* DLList<T>::findNode(const T key) {
DLNode* temp = new DLNode;
for (temp = first; temp != NULL; temp = temp->getNext()) {
if (temp->getData() == key)
return temp;
}
return NULL;
}
template<class T>
void DLList<T>::swap() {
DLNode* last = new DLNode;
//navigate to second to last node
for (last = first; last->getNext() != NULL; last = last->getNext()) {
}
last->getPrev()->setNext(first);
first->setPrev(last->getPrev());
last->setPrev(NULL);
last->setNext(first->getNext());
first->getNext()->setPrev(last);
first->setNext(NULL);
first = last;
}
} /* namespace lab7 */
#endif /* DLLIST_H_ */
另外还有一些我不理解的错误：
In file included from ../Lab7PartC/Lab7B.cpp:13:0:
../Lab7PartC/DLList.h:14:11: error: ‘DLNode’ is not a template
../Lab7PartC/DLList.h:14:18: error: ‘T’ was not declared in this scope
../Lab7PartC/DLList.h: In member function ‘void lab7::DLList<T>::insert(T)’:
../Lab7PartC/DLList.h:43:9: error: ‘lab7::DLNode’ is not a template
../Lab7PartC/DLList.h:47:13: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h: In member function ‘void lab7::DLList<T>::print()’:
../Lab7PartC/DLList.h:54:25: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:55:24: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h: In member function ‘bool lab7::DLList<T>::search(T)’:
../Lab7PartC/DLList.h:62:28: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:64:53: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:65:21: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h: In member function ‘bool lab7::DLList<T>::searchandremove(T)’:
../Lab7PartC/DLList.h:73:28: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:74:28: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:75:32: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:78:28: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:79:28: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:80:21: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:81:21: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:84:21: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:87:21: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:89:25: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h: In member function ‘lab7::DLNode* lab7::DLList<T>::findNode(T)’:
../Lab7PartC/DLList.h:99:28: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:100:53: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:101:21: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h: In member function ‘void lab7::DLList<T>::swap()’:
../Lab7PartC/DLList.h:109:28: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:111:32: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:111:64: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:113:13: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:114:14: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:114:28: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:115:13: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:116:13: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:116:28: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:117:14: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:118:14: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h: In member function ‘void lab7::DLList<T>::insert(T) [with T = int]’:
../Lab7PartC/Lab7B.cpp:23:26: instantiated from here
../Lab7PartC/DLList.h:44:9: error: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: error: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h: In member function ‘bool lab7::DLList<T>::searchandremove(T) [with T = int]’:
../Lab7PartC/Lab7B.cpp:34:32: instantiated from here
../Lab7PartC/DLList.h:91:13: warning: possible problem detected in invocation of delete operator:
../Lab7PartC/DLList.h:75:17: warning: ‘toDelete’ has incomplete type
../Lab7PartC/DLList.h:14:11: warning: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:91:13: note: neither the destructor nor the class-specific operator delete will be called, even if they are declared when the class is defined.
../Lab7PartC/DLList.h: In destructor ‘lab7::DLList<T>::~DLList() [with T = int]’:
../Lab7PartC/Lab7B.cpp:46:1: instantiated from here
../Lab7PartC/DLList.h:38:9: warning: possible problem detected in invocation of delete operator:
../Lab7PartC/DLList.h:38:9: warning: invalid use of incomplete type ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:14:11: warning: forward declaration of ‘struct lab7::DLNode’
../Lab7PartC/DLList.h:38:9: note: neither the destructor nor the class-specific operator delete will be called, even if they are declared when the class is defined.
答案 0 :(得分：1)
首先，模板应该只在头文件中实现。见Why can templates only be implemented in the header file?
现在，DLNode不是一个类，它是一个类模板，所以它应该总是有一个模板参数，即DLNode<T>或DLNode<int>。现在，您可能想知道为什么不在类体中执行此操作，例如void setNext(DLNode* n)，这是因为该参数隐含在类范围内。
我写的内容似乎令人困惑，但这就是一切应该看起来的样子：
template<class T>
DLNode<T>::DLNode() {
data = 0;
next = NULL;
prev = NULL;
}
template<class T>
DLNode<T>::DLNode(T d) {
data = d;
next = NULL;
prev = NULL;
}
template<class T>
DLNode<T>::DLNode(T d, DLNode* n, DLNode* p) {
data = d;
next = n;
prev = p;
}
template<class T>
DLNode<T>::~DLNode() {
delete next;
}
正如我所说，这段代码需要在头文件而不是cpp文件中。虽然一旦你这样做，在类体之外定义它们变得毫无意义，所以只需在类体内定义所有内容：
namespace lab7 {
template<class T>
class DLNode {
public:
DLNode() {
data = 0;
next = NULL;
prev = NULL;
}
// ...
};
} /* namespace lab7 */
答案 1 :(得分：0)
//forgot something here?
DLNode::~DLNode() {
delete next;
}
构造函数相同。 在每个函数定义之前使用模板声明。
答案 2 :(得分：0)
至少有两个问题：默认构造函数和析构函数声明不以template<class T>开头。