c++ - 字段 'class' 有一个不兼容的 'class'

Question

我收到这些错误:

node.h:12:2: error: 'Student' does not name a typeStudent student; 
node.h:17:14: error: 'Student' does not name a typeNode( const Student& );
node.h:20:25: error: 'Student' does not name a type
void setStudent( const Student& );
node.h:21:2: error: 'Student' does not name a type
Student getStudent() const { return student; }

这是我从 student.h 中删除 include node.h 时发生的情况

node.cpp:13: first defined here
node.cpp.o: In function `Node::~Node()'
node.cpp:13: multiple definition of `Node::Node()'
node.cpp:13: first defined here
node.cpp.o: In function `Node::~Node()':
node.cpp:17: multiple definition of `Node::Node(Node const&)'
main.cpp.o:node.cpp:17: first defined here
node.cpp.o: In function `Node::~Node()':
node.cpp:17: multiple definition of `Node::Node(Node const&)'
main.cpp.o:C:node.cpp:17: first defined here
node.cpp.o: In function `Node::Node(Student const&)':
node.cpp:25: multiple definition of `Node::Node(Student const&)'
node.cpp:25: first defined here

在 node.h 中

#pragma once
#ifndef node_h
#define node_h
#include "student.h"
class Node
{
private:
   Student student; 
   Node* nextPtr;
   Node* prevPtr;
public:
   Node();
   Node( const Student& );
   Node( const Node& );
   virtual ~Node() {}
   void setStudent( const Student& );
   Student getStudent() const { return student; } //second error here
   //linked list needs to be set as a friend
   friend class dblinkedlist;
};
#endif

在 student.h 中我不明白为什么这不能正常工作我已经尝试多次更改代码，但无济于事。

  #ifndef STUDENT_H
  #define STUDENT_H
  #include <stdio.h>
  #include <string>
  #include "node.h"
  using namespace std;
 class Student 
 {
 private:
    string FirstName;
    string LastName;
    int idNumber;
    double Gpa;
 public:
    //constructors
    Student();
    Student( string, string, int, double );
    //copy construtor
    Student( const Student& );
    //destructor
    virtual ~Student(){}
    //set/get for private data
    void setidNumber( int i );
    int getidNumber() const { return idNumber; }
    void setFirstName( string );
    string getFirstName( string ) const { return FirstName; }
    void setLastName( string );
    string getLastName( string ) const { return LastName; }
    void setGpa( double g );
    double getGpa( double ) const { return Gpa; }
    void setStudent( const Student& );
    Student getStudent() const { return *this; }
    //overloaded assignment
    Student operator=( const Student& );
    //overloaded << and >>
    friend ostream& operator<<( ostream&, const Student& );
    friend istream& operator>>( istream&, Student& );
    //overloaded ==
    friend bool operator==( const Student&, const Student& );
    //make Node class a friend
    friend class Node;
  }; 
 #endif

我尝试了一些其他方法来修复错误，但没有得出结论，非常感谢任何帮助。

Answer 1

问题是 student.h 包含了 node.h，它需要 Student 的完整定义，所以它包含了 student.h，但是由于我们已经在处理 student.h，header guards 已经定义了，什么也没有，所以它在 node.h 中继续并到达 Student 变量，但它尚未定义，因为即使我们从 student.h 开始，我们也从未真正到达 Student 类。

解决方案是从 student.h 中删除 node.h 的包含