（c ++）节点标头的语法错误[重复]

Question

我收到此标头的所有语法错误和令牌错误。

#pragma once
#include "Book.h"
#include <string>
using namespace std;
/**
* This is a node class, they will hold object
* data and nodes will be utilized in List class
*/
class Node
{
public:
    /**
    * Purpose: Default constructor
    * Parameters: none
    * Returns: none
    * Pre-conditions: none
    * Post-conditions: NULL node is added to Linked List
    */
    Node();

    /**
    * Purpose: De-constructor
    * Parameters: none
    * Returns: none
    * Pre-conditions: none
    * Post-conditions: Node is deleted
    */
    ~Node();

    /**
    * Purpose: Parameterized constructor
    * Parameters: Book
    * Returns: none
    * Pre-conditions: none
    * Post-conditions: node is added to Linked List
    *                  with data
    */
    Node(Book* B);

    /**
    * Purpose: Name getter
    * Parameters: none
    * Returns: Book
    * Pre-conditions: Item name is not NULL
    * Post-conditions: none
    */
    Book* getBook();

    /**
    * Purpose: Next node getter
    * Parameters: none
    * Returns: Pointer for next node in list
    * Pre-conditions: Must have another node in list ahead of this
    * Post-conditions: none
    */
    Node* getNextNode();

    /**
    * Purpose: Next node setter
    * Parameters: pointer for next node in list
    * Returns: none
    * Pre-conditions: none
    * Post-conditions: List has new node ahead of this
    */
    void setNextNode(Node* a);

private:
    Book* thisBook;
    string itemName;
    string itemType;
    int itemNum;
    Node* nextNode;
};

一切似乎都井然有序，但我收到了这些错误

Error   C2061   syntax error: identifier 'Book'     38  

Error   C2535   'Node::Node(void)': member function already defined or declared     38  

Error   C2143   syntax error: missing ';' before '*'    47  

Error   C4430   missing type specifier - int assumed. Note: C++ does not support default-int    47  

Error   C2238   unexpected token(s) preceding ';'   47  

Error   C2143   syntax error: missing ';' before '*'    68  

Error   C4430   missing type specifier - int assumed. Note: C++ does not support default-int    68  

Error   C2238   unexpected token(s) preceding ';'   68  

我正在创建一个链接列表，这些类型的错误也出现在我的 List.h 文件中。我错过了某种减速吗？至于第二个错误，它指向了参数化的构造函数。

编辑：书籍定义代码

#pragma once
#include "Node.h"
#include "List.h"
#include <string>
using namespace std;

/**
* Class designed to store information
* of a book. This class is the BASE.
*/
class Book
{
private:
    string author;
    string title;
    double price;

public:

    /**
    * Purpose: Default constructor
    * Parameters: none
    * Returns: none
    * Pre-conditions: none
    * Post-conditions: none
    */
    Book();

    /**
    * Purpose: Constructor
    * Parameters: author, address, price
    * Returns: none
    * Pre-conditions: none
    * Post-conditions: variables saved
    */
    Book(string, string, double);

    /**
    * Purpose: Getter for Author class
    * Parameters: none
    * Returns: Author class
    * Pre-conditions: none
    * Post-conditions: none
    */
    string getAuthor();

    /**
    * Purpose: Getter for title
    * Parameters: none
    * Returns: title
    * Pre-conditions: title must have been saved
    * Post-conditions: none
    */
    string getTitle();

    /**
    * Purpose: Getter for price
    * Parameters: none
    * Returns: price
    * Pre-conditions: price must have been saved
    * Post-conditions: none
    */
    double getPrice();
};

Answer 1

如果这两个标头都包含在同一个文件中，根据顺序，它将尝试在Book 之前定义Node

为了解决这种依赖关系，要么确保它们包含在正确的顺序中，要么声明Book而不在class Node之前定义它

class Book;

class Node
{
    ...
};