Re: Tables and the API

[Jason Murdick <wjmurdick@...>]

Wow!  Thank you... The first method definitely sounds like it would be
the way to go.  I appreciate the quick response.  Oh, and your C++
looks great to me.

Jason



On Mon, 14 Mar 2005 12:27:07 -0300, Romulo Bahiense
<romulo@icontroller.com.br> wrote:
> > Has anyone done this previously?
>        Of course :)
> 
> > Or have a good example?
> 
>        For what I understood, you want to make a table for the result set and
> one table for each record. It is quite simple, but I don't (and probably
> no one) recommend you to do so. It's very expensive to create a table
> for each record and then gc them all.
> 
>        I propose you to make a function called, say, dbfetch which receives a
> handle for the resultset and an optional table as second parameter. When
> called, if the second argument is a table, then the function will just
> replace that table's values for the new ones. If the second argument is
> not a table, then create a new one, populate it, and return.
> 
>        I'm not a C/C++ programmer, but I'll try my best to show you an example:
> 
> int lua_db_fetch(lua_State *L)
> {
>        /* Check here if the 1st parameter is your data object */
> 
>        // Now we check if the second argument is a table
>        if(!lua_istable(L,2))
>        {
>                // Yes, it is. Now we have to make sure it is
>                // on the top of the stack.
>                lua_settop(L,1);
>                lua_newtable(L);
>        }
> 
>        // iterate over dataset's fields
>        for (int i = 0; i < MYRESULTSET->GETFIELDCOUNT(); i++)
>        {
>                // Push the name of the field as key
>                lua_pushstring(L, MYRESULTSET->GETFIELDNAME(i));
> 
>                // Here you would push the appropriate value
>                // according to field's type.
>                lua_pushstring(L, MYRESULTSET->GETFIELDVALUE(i));
> 
>                // Now we push the key/value into table.
>                lua_settable(L, 2);
>        }
> 
>        // Returns the table, no matter if we created it or it was
>        // passed as a parameter.
>        return 1;
> }
> 
>        If you really want to have a table for the dataset and one table for
> each record, do something like:
> 
> int lua_db_query(lua_State *L)
> {
>        DATASET ds = MYDB->QUERY(lua_tostring(L, 1));
> 
>        // Create the core table, the one which will hold all
>        // records.
>        lua_newtable(L);
> 
>        int count = 1;
> 
>        // Iterate over all records of the dataset
>        while(ds->next())
>        {
>                lua_pushnumber(L,count++);
>                lua_newtable(L);
>                for (int i = 0; i < ds->GETFIELDCOUNT(); i++)
>                {
>                        lua_pushstring(L, ds->GETFIELDNAME(i));
>                        lua_pushstring(L, ds->GETFIELDVALUE(i));
>                        lua_settable(L, -3);
>                }
>                lua_settable(L, -3);
>        }
>        return 1;
> }
> 
>        Please note that it would be possible to use << lua_rawseti(L, count++,
> -2); >> instead of the last << lua_rawset(L, -3); >> but I choosed to do
> so because I think it is more intuitive at first :)
> 
> Hope it helped a bit.
> 
> --rb
>