c - 如何从指针到指针引用变量的值？

Question

我有一个结构:

 struct room;
 ...
 /*some more structs */

 typedef struct {     
   int state;
   int id;
   struct room* north;
   struct room* south;
   struct room* east;
   struct room* west;
   creature* creatures[10];
 } room;

还有一个打印内容的函数:

 void printContentsOfRoom(room* r) {
   printf("\nRoom %d:\n", r->id);
   printf("\tState: %s\n", getState(r));
   printf("\n\tNeighbors:\n");
   if (r->north.id != -1)
     printf("\t    North: Room %d\n",((room*)r->north)->id);
   if (r->east.id != -1)
     printf("\t    East: Room %d\n",((room*)r->east)->id);
   if (r->south.id != -1)
     printf("\t    South: Room %d\n",((room*)r->south)->id);
   if (r->west.id != -1)
     printf("\t    West: Room %d\n",((room*)r->west)->id);
   printf("\n\tCreatures:\n");
   for (int i = 0; i < 10; i++) {
     creature* c = (creature*)r->creatures[i];
     if (c) {
       if (c == pc)
     printf("\t    %s\n",getType(c));
       else
     printf("\t    %s %d\n",getType(c),c->id);
     }
   }
 }

我试图将房间 ID 设置为 -1(在程序运行时设置)，它不会打印有关该房间的信息。编译时，我收到错误“请求非结构或 union 中的成员‘id’。”

此外，我尝试设置 if 条件 r->north->id，并返回错误“取消引用指向不完整类型'struct room'的指针”

Answer 1

我认为你想要做这样的前向声明:

typedef struct room room;

struct room{
    .
    .
    .
};

然后你可以使用r->north->id。看到这个问题:How to define a typedef struct containing pointers to itself?