使用 Lua 表 C API 创建一个简单的表 [英] Creating a simple table with Lua tables C API

问题描述

我正在运行一个总是返回 4 行的 MySQL 查询:

I'm running a MySQL query which always returns 4 rows:

row->name、row->date、row->ip、row->custom

我想要实现的是基于上述结果创建一个简单的表格，它看起来像:

What I want to achieve is create a simple table basing on the above results so it would look like:

{
     "name" = result of row->name,
     "date" = result of row->date,
     "ip"   = result of row->ip,
     "custom" = result of row->custom
}

我尝试了多种可能性，但发布的示例确实多种多样，而且我在使其工作时遇到了问题.

I have tried multiple possibilities, but the examples posted are really varied and I got a problems making it working.

我最后一次失败的尝试:

My last unsuccessful try:

lua_createtable(L, 0, 4);
top = lua_gettop(L);
lua_pushstring(L, "name");
lua_pushstring(L, row->name);
lua_pushstring(L, "date");
lua_pushnumber(L, row->date);
lua_pushstring(L, "ip");
lua_pushstring(L, row->ip);
lua_pushstring(L, "custom");
lua_pushstring(L, row->custom);
lua_settable(L, top);

推荐答案

正如我在评论中提到的，lua_settable() 只处理一对 key, value.如果您需要更多，必须重复.

As I mentioned in comment, lua_settable() takes care only of one key, value pair. Must repeat that if You need more.

我更喜欢像这样保存 Lua 堆栈空间:

I'd prefer saving the Lua stack space like this:

lua_createtable(L, 0, 4);

lua_pushstring(L, "name");
lua_pushstring(L, row->name);
lua_settable(L, -3);  /* 3rd element from the stack top */

lua_pushstring(L, "date");
lua_pushstring(L, row->date);
lua_settable(L, -3);

lua_pushstring(L, "ip");
lua_pushstring(L, row->ip);
lua_settable(L, -3);

lua_pushstring(L, "custom");
lua_pushstring(L, row->custom);
lua_settable(L, -3);

/* We still have table left on top of the Lua stack. */

此外，您可以编写某种 C 结构迭代器或其他东西.

Also, You could write some kind of C struct iterator or something.

注意:如果这是用于某种 Lua 包装器 - 您应该确保 标准化这样做的方式.在以下示例中，应用了 @lhf 注释，将其缩短一点:

NOTE: if this is for some kind of Lua wrapper - You should ensure standardized way of doing that. In the following example applied @lhf comment about shortening it a bit:

int 
l_row_push(lua_State *l)
{
    lua_createtable(L, 0, 4); /* creates and pushes new table on top of Lua stack */

    lua_pushstring(L, row->name); /* Pushes table value on top of Lua stack */
    lua_setfield(L, -2, "name");  /* table["name"] = row->name. Pops key value */

    lua_pushstring(L, row->date);
    lua_setfield(L, -2, "date");

    lua_pushstring(L, row->ip);
    lua_setfield(L, -2, "ip");

    lua_pushstring(L, row->custom);
    lua_setfield(L, -2, "custom");

    /* Returning one table which is already on top of Lua stack. */
    return 1;
}

修复了 lua_setfield() 的使用@lhf 注意.谢谢！

Fixes usage of lua_setfield() by @lhf note. Thanks!

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