8.3 KiB
8.3 KiB
6.绘制地图
作为一个 RPG 游戏怎么能没有地图呢，是时候绘制地图了！
绘制地图的最佳工具始终是：一支铅笔和一张纸。基本地图由位置（矩形）组成，由道路（箭头）连接。我们已经在第 3 章中创建了位置，现在我们将开始添加道路。
在虚拟世界中，“道路”可能是连接两个位置的任何东西：一条路，一扇门，沙漠中。基本上，一段经文具有以下属性：
- 起点（位置）。
- 目标（位置）。
- 叙述性描述，例如“森林小径”。
- 在 go 命令中往哪里走的描述性标记
考虑到这些属性，第 4 章中定义的结构对象就非常适合存储道路了。事实上，一个道路与一个项目或 NPC 并没有太大的不同，它作为“可见出口”存在于某个位置（该位置是起点）。它只是与某些命令的行为不同，特别是命令“go”：应用于道路，go将改变玩家的位置。
struct object {
const char *description;
const char *tag;
struct object *location;
struct object *destination;
};
注意：
- 显然，目的地在大多数其他对象（物品，NPC）中都没有使用
- 通道总是朝一个方向运行;要双向连接两个位置，我们总是必须创建两个单独的通道。乍一看，这似乎很笨拙，但它确实给了我们很大的灵活性来完善命令“go”的行为
- 在大地图上，你可能会发现手动创建所有通道很乏味。所以，我强烈建议你使用自定义工具生成地图中重复性更强的部分。这里不会介绍这一点，但您可能会在第 9 章中找到一些灵感，我们将在其中讨论自动胜场。
思考题：为什么创建两个通道可以使我们的程序更加灵活？
接下来我们将展开对象数组
object.h
typedef struct object {
const char *description;
const char *tag;
struct object *location;
struct object *destination;
} OBJECT;
extern OBJECT objs[];
#define field (objs + 0) //是不是觉得这个很熟悉
#define cave (objs + 1)
#define silver (objs + 2)
#define gold (objs + 3)
#define guard (objs + 4)
#define player (objs + 5)
#define intoCave (objs + 6)
#define exitCave (objs + 7)
#define endOfObjs (objs + 8)
object.c
#include <stdio.h>
#include "object.h"
OBJECT objs[] = {
{"an open field" , "field" , NULL , NULL },
{"a little cave" , "cave" , NULL , NULL },
{"a silver coin" , "silver" , field, NULL },
{"a gold coin" , "gold" , cave , NULL },
{"a burly guard" , "guard" , field, NULL },
{"yourself" , "yourself", field, NULL },
{"a cave entrance", "entrance", field, cave },
{"an exit" , "exit" , cave , field }
};
我们将在 misc.c 中添加一个小的帮助函数，以确定两个给定位置之间是否存在通道。
misc.h
extern OBJECT *getPassage(OBJECT *from, OBJECT *to);
extern OBJECT *actorHere(void);
extern int listObjectsAtLocation(OBJECT *location);
misc.c
#include <stdio.h>
#include "object.h"
OBJECT *getPassage(OBJECT *from, OBJECT *to)
{
if (from != NULL && to != NULL)
{
OBJECT *obj;
for (obj = objs; obj < endOfObjs; obj++) //寻找物品之间是否具有通道
{
if (obj->location == from && obj->destination == to)
{
return obj; //找到了
}
}
}
return NULL;//找不到
}
OBJECT *actorHere(void)
{
OBJECT *obj;
for (obj = objs; obj < endOfObjs; obj++)
{
if (obj->location == player->location && obj == guard)
{
return obj;
}
}
return NULL;
}
int listObjectsAtLocation(OBJECT *location)
{
int count = 0;
OBJECT *obj;
for (obj = objs; obj < endOfObjs; obj++)
{
if (obj != player && obj->location == location)
{
if (count++ == 0)
{
printf("You see:\n");
}
printf("%s\n", obj->description);
}
}
return count;
}
我们将在命令“go”的实现中使用新功能getPassage来确定是否存在可以将玩家带到所需位置的通道。
location.h
extern void executeLook(const char *noun);
extern void executeGo(const char *noun);
location.c
#include <stdio.h>
#include <string.h>
#include "object.h"
#include "misc.h"
#include "noun.h"
void executeLook(const char *noun)
{
if (noun != NULL && strcmp(noun, "around") == 0)
{
printf("You are in %s.\n", player->location->description);
listObjectsAtLocation(player->location);
}
else
{
printf("I don't understand what you want to see.\n");
}
}
void executeGo(const char *noun)
{
OBJECT *obj = getVisible("where you want to go", noun);
if (obj == NULL)
{
// already handled by getVisible
}
else if (getPassage(player->location, obj) != NULL)
//go只会在有地方的时候才会运行起来
{
printf("OK.\n");
player->location = obj;
executeLook("around");
}
else if (obj->location != player->location)
{
printf("You don't see any %s here.\n", noun);
}
else if (obj->destination != NULL)
{
printf("OK.\n");
player->location = obj->destination;
executeLook("around");
}
else
{
printf("You can't get much closer than this.\n");
}
}
我们还将使用新功能getPassage来确定从玩家站立的位置是否可以看到某个位置。未通过通道连接到当前位置的位置不被视为可见。
noun.h
extern OBJECT *getVisible(const char *intention, const char *noun);
extern OBJECT *getPossession(OBJECT *from, const char *verb, const char *noun);
noun.c
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include "object.h"
#include "misc.h"
static bool objectHasTag(OBJECT *obj, const char *noun)
{
return noun != NULL && *noun != '\0' && strcmp(noun, obj->tag) == 0;
}
static OBJECT *getObject(const char *noun)
{
OBJECT *obj, *res = NULL;
for (obj = objs; obj < endOfObjs; obj++)
{
if (objectHasTag(obj, noun))
{
res = obj;
}
}
return res;
}
OBJECT *getVisible(const char *intention, const char *noun)
{
OBJECT *obj = getObject(noun);
if (obj == NULL)
{
printf("I don't understand %s.\n", intention);
}
else if (!(obj == player ||
obj == player->location ||
obj->location == player ||
obj->location == player->location ||
getPassage(player->location, obj) != NULL || //检查两个位置是否相邻
(obj->location != NULL &&
(obj->location->location == player ||
obj->location->location == player->location))))
{
printf("You don't see any %s here.\n", noun);
obj = NULL;
}
return obj;
}
OBJECT *getPossession(OBJECT *from, const char *verb, const char *noun)
{
OBJECT *obj = NULL;
if (from == NULL)
{
printf("I don't understand who you want to %s.\n", verb);
}
else if ((obj = getObject(noun)) == NULL)
{
printf("I don't understand what you want to %s.\n", verb);
}
else if (obj == from)
{
printf("You should not be doing that to %s.\n", obj->description);
obj = NULL;
}
else if (obj->location != from)
{
if (from == player)
{
printf("You are not holding any %s.\n", noun);
}
else
{
printf("There appears to be no %s you can get from %s.\n",
noun, from->description);
}
obj = NULL;
}
return obj;
}
显然，此示例中的地图是微不足道的：只有两个位置，并且它们在两个方向上都连接在一起。第 12 章将增加第三个地点。
思考题：你能否绘制一张更精细的地图，并将其变成对象列表（位置和通道）
注：不用当成任务，自行实验即可
输出样例
Welcome to Little Cave Adventure. You are in an open field. You see: a silver coin a burly guard a cave entrance
--> go entrance OK. You are in a little cave. You see: a gold coin an exit
--> go exit OK. You are in an open field. You see: a silver coin a burly guard a cave entrance
--> go cave OK. You are in a little cave. You see: a gold coin an exit
--> quit
Bye!