Question

我的主要（全局）标题中的班级延迟中有几个循环声明案例。

#include <cstdlib>
#include <iostream>

using namespace std;


enum piece_t {BLACK, WHITE, EMPTY, WALL}; //wall is area out side of board (board array is 21x21 but only 19x19 is playable)
enum dir_t {ABOVE,BELOW,LEFT, RIGHT}; //shall i overload ! or - operatior? !LEFT==RIGHT?


struct nextPoint_t  //should be implimented with references, but need to practice pointer
{ 
  point_t* above;
  point_t* below;
  point_t* left;
  point_t* right;

};




class point_t
{
 private:
  piece_t mType; //what sort of point this is
  int mLiberties;
  nextPoint_t  mAdjacent; // points to adjacent points

  bool mLibertiesCounted; // keeps track of if liberties have been counted, for mCountLiberites() (sets), is reset by mUpdateLiberites(); 

  int mCountLiberties(); //counts this point's liberites, by calling count on mAdjacent points etc.
  void mSetPos(int xPos, int yPos, board_t theBoard); //sets up mAdjacent to point to adjacent points,
  void mSetStructureLiberties(int numLibs); // Sets this squares liberites then calls this on all adjacent squares 


 public:
  point_t ();//  parameterless constructor, for arrays
  void mSetUp(int xPos, int yPos, board_t theBoard);// sets up mType then calles setPos iFF not WALL type
  point_t (int xPos, int yPos, board_t theBoard); //constructor, takes it's position in the grid as a parameter

  void mUpdateLiberties(); // calles countLiberties then, updates liberites on whole of connected structure, by operating pon all conencted points



};

class board_t 
{
 private:
  point_t mArray [21][21];


 public:
  board_t(); //constructor, sets up board by operating on the point_t's

};

不要担心我的阅读中的评论，我知道我的意思。

我以为我可以用前向声明修复它，但它们似乎不起作用，它只是认为我正在重新定义类

Answer 1

好的，在考虑了评论并自己做测试后，真正的答案是：你必须使用前向声明，不能再使用。：）

#include <cstdlib>
#include <iostream>

class point_t;
class board_t;

/* Rest of the code stay the same */

Answer 2

如果你在结构之前写

class point_t;

应该这样做。

虽然我不太清楚为什么你这样组织你的班级。您的电路板中已经有一个数组mArray，因此没有必要指向每个point_t内的相邻点。

编辑：正如另一张海报所说，在您需要使用指针之前。

Answer 3

您的代码中的转发引用似乎是board_t和point_t，这是通过向前声明它们来解决的。

由于您在board_t的成员函数声明中引用point_t，因此无法立即在point_t中定义成员函数。他们的定义必须在定义board_t后出现。因此，您必须将函数的定义移动到cpp文件中，或者您必须在board_t的定义后的标题中移动它们的定义，无论哪个更适合您。 point_t仅用作nextPoint_t中的指针类型，因此我们在此处没有相同的问题：

class point_t; // used by nextPoint_t class board_t; // used by point_t struct nextPoint_t //should be implimented with references, but need to practice pointer { point_t* above; // goes without problems - doesn't need definition of point_t point_t* below; point_t* left; point_t* right; }; class point_t { private: piece_t mType; int mLiberties; nextPoint_t mAdjacent; bool mLibertiesCounted; int mCountLiberties(); void mSetPos(int xPos, int yPos, board_t theBoard); void mSetStructureLiberties(int numLibs); public: point_t (); void mSetUp(int xPos, int yPos, board_t theBoard); point_t (int xPos, int yPos, board_t theBoard); void mUpdateLiberties(); }; class board_t { private: point_t mArray [21][21]; public: board_t(); };

标题末尾的定义类似于

// define it either inline in the header, or non-inline in a cpp file inline void point_t::mSetPos(int xPos, int yPos, board_t theBoard) { /* some work... */ } // same for mSetUp...

尽管如此，我建议您使用const引用将该板传递给point_t的成员函数，但不是您的代码工作的要求。声明与不完整的参数类型一致。

Answer 4

只需添加以上struct nextPoint_t

即可

enum piece_t {BLACK, WHITE, EMPTY, WALL};
enum dir_t {ABOVE,BELOW,LEFT, RIGHT}; 

class point_t;
class board_t;

struct nextPoint_t
{ 
  point_t* above;
  point_t* below;
  point_t* left;
  point_t* right;
};

并将对board_t的任何引用更改为board_t *

void mSetUp(int xPos, int yPos, board_t* theBoard);

Answer 5

#include <cstdlib>
#include <iostream>

enum piece_t {BLACK, WHITE, EMPTY, WALL}; //wall is area out side of board (board array is 21x21 but only 19x19 is playable)
enum dir_t {ABOVE,BELOW,LEFT, RIGHT}; //shall i overload ! or - operatior? !LEFT==RIGHT?

class point_t;

struct nextPoint_t  //should be implimented with references, but need to practice pointer
{ 
  point_t* above;
  point_t* below;
  point_t* left;
  point_t* right;

};


class board_t;

class point_t
{
 private:
  piece_t mType; //what sort of point this is
  int mLiberties;
  nextPoint_t  mAdjacent; // points to adjacent points

  bool mLibertiesCounted; // keeps track of if liberties have been counted, for mCountLiberites() (sets), is reset by mUpdateLiberites(); 

  int mCountLiberties(); //counts this point's liberites, by calling count on mAdjacent points etc.
  void mSetPos(int xPos, int yPos, const board_&t theBoard); //sets up mAdjacent to point to adjacent points,
  void mSetStructureLiberties(int numLibs); // Sets this squares liberites then calls this on all adjacent squares 


 public:
  point_t ();//  parameterless constructor, for arrays
  void mSetUp(int xPos, int yPos, const board_t& theBoard);// sets up mType then calles setPos iFF not WALL type
  point_t (int xPos, int yPos, const board_t& theBoard); //constructor, takes it's position in the grid as a parameter

  void mUpdateLiberties(); // calles countLiberties then, updates liberites on whole of connected structure, by operating pon all conencted points



};

class board_t 
{
 private:
  point_t mArray [21][21];


 public:
  board_t(); //constructor, sets up board by operating on the point_t's

};

C ++循环声明

5 个答案: