How to return a multidimensional table from C function to lua?

Question

I need to return a table to Lua like this:

{
    [0] = { ["field1"] = "1", ["field2"] = "2" , ["field3"] = "3" },
    [1] = { ["field1"] = "10" , ["field2"] = "20", ["field3"] = "30" }
}

But from a C perspective and using the lua_* functions Also, the 0 and 1 are just an example, it might contain more arrays like those. Anyone can help me please?

Kamiccolo · Accepted Answer · 2015-12-09T19:00:38.903

Simple example using lua_createtable(), lua_pushnumber(), lua_setfield() and lua_settable().

I assumed that You're writing some kind of wrapper. But still, it's almost pretty the same.

/* Pushes multidimentional table on top of Lua VM stack. */
int
l_push_multidim_table(lua_State *L)
{
    /* Creates parent table of size 2 array elements: */
    lua_createtable(L, 2, 0);

    /* Puts key of the first child table on-top of Lua VM stack: */
    lua_pushnumber(L, 1);

    /*Creates first child table of size 3 non-array elements: */
    lua_createtable(L, 0, 3);

    /* Fills the first child table: */
    lua_pushnumber(L, 1);
    lua_setfield(L, -2, "field1");

    lua_pushnumber(L, 2);
    /* setfield() pops the value from Lua VM stack. */
    lua_setfield(L, -2, "field2");

    lua_pushnumber(L, 3);
    lua_setfield(L, -2, "field3");

    /* Remember, child table is on-top of the stack.
     * lua_settable() pops key, value pair from Lua VM stack. */
    lua_settable(L, -3);

    /* Pushes they key value for the second child table: */
    lua_pushnumber(L, 2);

    /*Creates second child table of size  3 non-array elements: */
    lua_createtable(L, 0, 3);

    /* Fills the second child table: */
    lua_pushnumber(L, 10);
    lua_setfield(L, -2, "field1");

    lua_pushnumber(L, 20);
    lua_setfield(L, -2, "field2");

    lua_pushnumber(L, 30);
    lua_setfield(L, -2, "field3");

    /* Remember, child table is still on-top of the stack.
     * lua_settable pops the key, value pair from Lua VM stack
     * And puts child table into the parent. */
    lua_settable(L, -3);

    /* Returns number of output tables:
     * (1 multidimentional)            */
    return 1;
}

NOTE: In Lua array values usually starts at 1. So, I've canged Your example structure that way. All in all, it should work well.

How to return a multidimensional table from C function to lua?

1 Answers1