无法弄清楚为什么头文件中的私有成员在 cpp 文件中不起作用

Question

您好，我一直在到处寻找此问题的解决方案，并尝试了多种不同的方法在 .cpp 文件中定义 ListNode。由于某种原因，该结构无法与 .cpp 文件共享。任何帮助将不胜感激。 谢谢

.H 文件：

#ifndef SORTEDLIST_H
#define SORTEDLIST_H

#include "Student.h"

/*
 * SortedList class
 *
 * A SortedList is an ordered collection of Students.  The Students are ordered
 * from lowest numbered student ID to highest numbered student ID.
 */
class SortedList {

  public:

    SortedList();
    // Constructs an empty list.

bool insert(Student *s);
// If a student with the same ID is not already in the list, inserts 
// the given student into the list in the appropriate place and returns
// true.  If there is already a student in the list with the same ID
// then the list is not changed and false is returned.

Student *find(int studentID);
// Searches the list for a student with the given student ID.  If the
// student is found, it is returned; if it is not found, NULL is returned.

Student *remove(int studentID);
// Searches the list for a student with the given student ID.  If the 
// student is found, the student is removed from the list and returned;
// if no student is found with the given ID, NULL is returned.
// Note that the Student is NOT deleted - it is returned - however,
// the removed list node should be deleted.

void print() const;
// Prints out the list of students to standard output.  The students are
// printed in order of student ID (from smallest to largest), one per line

private:

// Since ListNodes will only be used within the SortedList class,
// we make it private.
struct ListNode {    
  Student *student;
  ListNode *next;
};

ListNode *head; // pointer to first node in the list
};

#endif

.CPP 文件：

#include <iostream>
#include "SortedList.h"

using namespace std;


SortedList::SortedList() : head(NULL){}



Student SortedList::*find(int studentID){
ListNode *current;
current = head;
if(current != NULL){
 while(current != NULL){
               if(current.student.getID() == studentID){
               return current.student;
               }
 current = current.next;
 }
}
return NULL;                   
}

相关错误： C:\Users\Charles\Desktop\SortedList.cpp 在函数 Student SortedList::* find(int)' 中： 12 C:\Users\Charles\Desktop\SortedList.cppListNode'未声明（首先使用此函数）

Answer 1

这句话是错误的：

Student SortedList::*find(int studentID) {

你把星星放在了错误的位置。这不是返回 Student* 的 SortedList::find 定义的序言。这是名为 find 的自由函数定义的序言，该函数返回 Student SortedList::*。 （一种不寻常但格式良好的“指向成员的指针”类型）。因为它不是 SortedList 成员方法，所以 SortedList 的内部声明都不在范围内，这就是为什么您会收到令人困惑的错误消息。

这是你应该写的：（

Student *
SortedList::find(int studentID)
{

没有必要将其分成三行，但会让其他人更容易阅读你的代码。）

Answer 2

您收到的编译器错误有点误导；您的问题与 ListNode 根本无关。您的 cpp 文件中存在语法错误：

Student *SortedList::find(int studentID)

这意味着 SortedList::find 返回一个指向学生的指针。

Answer 3

正确的签名是：

Student* SortedList::find(int studentID)

指针是返回类型的一部分，而不是方法名称的一部分。