使用 Lua C API 迭代表 [英] Iterating over table of tables with the Lua C API

问题描述

我正在尝试遍历 Lua 中的表并输出:

I'm trying to iterate over a table of tables in Lua and output:

• 每个表的键.
• 每个表中每个条目的键/值对.

代码如下:

void print_table(lua_State *L)
{
    lua_pushnil(L);
    while(lua_next(L, -2) != 0) {
    const char *key = lua_tostring(L, -2);
            if(lua_isstring(L, -1))
                printf("%s = %s", key, lua_tostring(L, -1));
            else if(lua_isnumber(L, -1))
                printf("%s = %d", key, lua_tonumber(L, -1));
            else if(lua_istable(L, -1)) {
                printf("%s", key);
                PrintTable(L);
            }
            lua_pop(L, 1);
        }
    }
}

这是我尝试输出的表之一的示例:

And here is an example of one of a table I'm trying to output:

s = {
        p = {
            n = "D",
            g = "1",
        },
        d = {
            l = "N",
            p = "N",
            u = "O",
            po = 100,
        },
        e = {
            {
                n = "B",
                l = "P",
                p = "P",
                u = "P",
                po = "P",
                pa = {
                    v = "4",
                    a = "U",
                    f = {
                        { name = "U", type = "U" },
                        { name = "A", type = "I" },
                        { name = "A", type = "I" },
                        { name = "P", type = "U" },
                        { name = "P", type = "U" },
                        { name = "P", type = "I" },
                        { name = "T", type = "U" },
                        { name = "D", type = "U" },
                        { name = "D", type = "I" },
                        { name = "S", type = "I" },
                        { name = "C", type = "U" },
                        { name = "G", type = "U" },
                        { name = "C", type = "F" },
                        { name = "C", type = "U" },
                    },
                },
                c = {
                    v = "1",
                    a = "",
                    f = {
                        { name = "B", type = "U" },
                        { name = "E", type = "F" },
                    },
                },
            },
        },
    }

函数在行中崩溃:

while(lua_next(L, -2) != 0)

由于索引无效.导致崩溃的脚本行是:

due to an invalid index. The line of script that causes the crash is:

{ name = "B", type = "U" },

我不得不承认，我对 Lua 中的堆栈并不十分熟悉，我曾尝试寻找类似的答案，但没有找到任何答案.有人知道我做错了什么吗?

I have to admit I'm not massively familiar with the stack in Lua, I've tried searching for similar answers and was unable to find any. Anyone know what I'm doing wrong?

谢谢！

添加工作版本以防有人感兴趣:

Added working version in case anyone is interested:

void print_table(lua_State *L)
    {
        if ((lua_type(L, -2) == LUA_TSTRING))
            printf("%s", lua_tostring(L, -2));

        lua_pushnil(L);
        while(lua_next(L, -2) != 0) {
            if(lua_isstring(L, -1))
                printf("%s = %s", lua_tostring(L, -2), lua_tostring(L, -1));
            else if(lua_isnumber(L, -1))
                printf("%s = %d", lua_tostring(L, -2), lua_tonumber(L, -1));
            else if(lua_istable(L, -1)) {
                print_table(L);
            }
            lua_pop(L, 1);
        }
    }

推荐答案

f = {
    { name = "B", type = "U" },
    { name = "E", type = "F" },
}

相当于:

f = {
    [1] = { name = "B", type = "U" },
    [2] = { name = "E", type = "F" },
}

当你在键上调用 lua_tostring 时，Lua 会将数字索引更改为字符串.

When you call lua_tostring on the key Lua changes the numeric index to a string.

const char *key = lua_tostring(L, -2);

lua_tostring 使用 lua_tolstring 和来自 手册:

如果值是数字，那么lua_tolstring也会把栈中的实际值改为字符串.(当在表遍历期间将 lua_tolstring 应用于键时，此更改会混淆 lua_next.)

If the value is a number, then lua_tolstring also changes the actual value in the stack to a string. (This change confuses lua_next when lua_tolstring is applied to keys during a table traversal.)

最好使用 lua_type 来检查键是否真的是字符串，因为 lua_isstring 只会告诉您堆栈值是否可以转换为字符串.您还可以推送密钥的副本并在副本上调用 lua_tostring.

Better to use lua_type to check if the key really is a string since lua_isstring will only tell you if the stack value can be converted into a string. You could also push a copy of the key and call lua_tostring on the copy.

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