如何在c++中构造带有struct定义的类的头文件

Question

如果我有一个包含结构体的类。如何在头文件中声明该结构?

见下面的例子。这样的语法正确吗?

context:我的教授有一个IList.h文件，我们必须在LinkedList类中实现它。这就是为什么我的例子中有继承语法

LinkedList.cpp

#include "LinkedList.h"

class LinkedList : public IList {
struct Node
{
int data;
struct Node *next;
}

};

LinkedList.h

#ifndef LINKED_LIST_
#define LINKED_LIST_
#include "IList.h"
class LinkedList: public IList
{
protected:
struct Node;

};

IList.h

//  Modified from code created by Frank M. Carrano and Timothy M. Henry.
//  Copyright (c) 2017 Pearson Education, Hoboken, New Jersey.
#ifndef I_LIST_
#define I_LIST_
class IList
{
public:
/** Constructor */
IList () : traverseCount(0) { }

/** Destroys object and frees memory allocated by object.
(See C++ Interlude 2) */
virtual ~IList () { }
/** Gets the current number of entries in this list.
@return The integer number of entries currently in the list. */
virtual int getCurrentSize() const = 0;

/** Sees whether this list is empty.
@return True if the list is empty, or false if not. */
virtual bool isEmpty() const = 0;

/** Adds a new entry to this list.
@post  If successful, newEntry is stored in the list and
the count of items in the list has increased by 1.
@param newEntry  The object to be added as a new entry.
@return  True if addition was successful, or false if not. */
virtual bool add(int newEntry) = 0;

/** Removes one occurrence of a given entry from this list,
if possible.
@post  If successful, anEntry has been removed from the list
and the count of items in the list has decreased by 1.
@param anEntry  The entry to be removed.
@return  True if removal was successful, or false if not. */
virtual bool remove(int anEntry) = 0;

/** Removes all entries from this list.
@post  List contains no items, and the count of items is 0. */
virtual void clear() = 0;

/** Tests whether this list contains a given entry.
@param anEntry  The entry to locate.
@return  True if list contains anEntry, or false otherwise. */
virtual bool contains(int anEntry) = 0;

/** Get the count of number of nodes traversed.
@return  The integer number of nodes traversed since last time the count was reset. */
virtual int getTraverseCount() const { return traverseCount; }

/** Reset the count of nodes traversed to zero. */
virtual void resetTraverseCount() { traverseCount = 0; }

protected:
int traverseCount;
}; // end IList
#endif

Answer 1

您需要在LinkedList类中至少重新声明IList的纯虚拟方法，否则LinkedList将是一个抽象类，因此编译器将不允许您实例化LinkedList对象:

// LinkedList.h
#ifndef LINKED_LIST_
#define LINKED_LIST_
#include "IList.h"
class LinkedList: public IList
{
public:
LinkedList();
virtual ~LinkedList();
virtual int getCurrentSize() const;
virtual bool isEmpty() const;
virtual bool add(int newEntry);
virtual bool remove(int anEntry);
virtual void clear();
virtual bool contains(int anEntry);
private:
struct Node
{
int data;
struct Node *next;
};
struct Node *first;
};
#endif

…那么你需要在LinkedList.cpp:

中为你的方法编写实际的代码

// LinkedList.cpp
#include "LinkList.h"
LinkedList :: LinkedList()
{
[... code goes here...]
}
LinkedList :: ~LinkedList()
{
[... code goes here...]
}
int LinkedList :: getCurrentSize() const
{
[... code goes here...]
}
bool LinkedList :: isEmpty() const
{
[... code goes here...]
}
bool LinkedList :: add(int newEntry)
{
[... code goes here...]
}
bool LinkedList :: remove(int anEntry)
{
[... code goes here...]
}
void LinkedList :: clear()
{
[... code goes here...]
}
bool LinkedList :: contains(int anEntry)
{
[... code goes here...]
}