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

中删除包含 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

#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 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，非常感谢您的帮助。

Answer 1

我对这两行深感困惑：

#include "student.h"
class Student;

我不认为第二个是必要的。

这是在说 "hey compiler, go get the definition of the class Student from this here header file so that I can use it in this class and you'll know about its members and methods and we will both be happy"，紧接着是 "hey compiler, forget about that complete class definition I just gave you, instead, I'm declaring that a class Student exists, but I'm only going to tell you more about it later"。编译器被正确地混淆了。

Answer 2

对于你的第二个（第一个？）错误，你有两个 headers 包括彼此。而且我不明白为什么，因为 Student 中对 Node 的唯一引用是将其添加为好友，而 Node 从 Student 中唯一使用的是 get 和 setStudent()，它们是 public 方法。我会尝试删除 friend class Node 和 #include "node.h" 以查看是否有所不同。

Answer 3

问题是 student.h 包含 node.h，它需要 Student 的完整定义，因此它包含 student.h，但由于我们已经在处理 student.h header guards 已经被定义但什么都没有，所以它在 node.h 中继续并到达一个 Student 变量，但它还没有被定义，因为即使我们从 student.h 开始，我们实际上从未找到学生 class.

解决方案是从 student.h

中删除 node.h 的包含

字段 'class' 有一个不兼容的 'class'

field 'class' has an incompatible 'class'

c++

compiler-errors

class

function

incompatibility