c++ - 使用结构作为参数 : Error: Struct not defined

Question

我正在创建一个类，我在其中定义了一个名为“Room”的结构，我在头文件中将其声明为私有(private)。我有几个公共(public)函数需要一个“房间”作为参数。当我编译(在 g++ 中)时，我收到一条错误消息:

Graph.h:42:17: error: "Room" has not been declared

这里是声明(现在是整个头文件):

#ifndef GRAPH_H
#define GRAPH_H


#include <iostream>
#include <string>
using namespace std;

class Graph {

public:


    // destructor
    ~Graph();

    // copy constructor
    Graph(const Graph &v);

     // assignment operator
     Graph & operator = (const Graph &v);

    //Create an empty graph with a potential
    //size of num rooms.
     Graph( int num );

        //Input the form:
    //int -- numRooms times
    //(myNumber north east south west) -- numRooms times.
    void input(istream & s);

    //outputs the graph as a visual layout
    void output(ostream & s) const;

    //Recursively searches for an exit path.
    void findPath( Room start );

    //Moves room N E S or W
    void move( Room &*room , String direction );

    //inputs the starting location.
    void inputStart( int start );

    //Searches the easyDelete array for the room with the
    //number "roomNumber" and returns a pointer to it.
    const Room * findRoom( int roomNumber );

private:

    struct Room
    {
        bool visted;
        int myNumber;

        Room *North;
        Room *East;
        Room *South;
        Room *West;
    };

    int numRooms;
    int _index;
    int _start;

    Room ** easyDelete;
    string * escapePath;

    Room * theWALL;
    Room * safety;
};

#endif

是否不允许使用头文件中定义的结构作为参数？如果是这样，解决方法是什么？

谢谢。

Answer 1

它在没有 private: header 的情况下编译得很好。你为什么有这个？结构是否在类内部声明？

编辑

在声明之前您已经使用过 Room:

const Room * findRoom( int roomNumber );

此外，您不能通过已声明的公共(public)方法返回 Room 对象，因为外部代码对此一无所知。

使用前需要预先声明:

class Graph {

public:

struct Room;

const Room * findRoom( int roomNumber );

struct Room
{
    bool visted;
    int myNumber;

    Graph::Room *North;
    Graph::Room *East;
    Graph::Room *South;
    Graph::Room *West;
};

Room room;
};

int main (){

  Graph x;

  return 0;
}

或者您可以将第二个 private 向上移动，在 public 部分之上。