How to get results from a Delphi function called by Lua

Question

I am creating a function in Delphi to be able to use it with Lua. I have managed to create a procedure (or a function without taking results) and it works perfect. The problem is that now I want to get results of that function (not a procedure anymore) from Delphi into Lua. I've read some codes out there but couldn't make it work.

My function looks like this:

function TLuaScripter.getsetting(LuaState: TLuaState):TluaState; var path,stri: string; i:integer; begin //getsetting('Targeting/TargetingEnabled') path := Lua_ToString(LuaState, 1); //we get the string 'Targeting/..." Lua_Pop(LuaState,1); //we put it in stack (so we can clean it) stri:= tree.GETsetting(path); //this function gets, for example "No" lua_pushlstring(LuaState,Pansichar(ansistring(stri)),length(stri)); //I pass it to the lua stack //showmessage(Lua_ToString(LuaState,1));--> this shows the result I need in a msgbox result:= LuaState; end;

so now if I use in my Lua Console

getsetting('Targeting/TargetingEnabled')

I am able to get the result in a msgbox (uncommenting the "Showmessage...") but that function doesn't return anything in Lua! If I write

print(getsetting('Targeting/TargetingEnabled'))

I get a Nil value in Lua.

You should register a function of type lua_CFunction which returns number of results pushed into stack. So, change return type to Integer and properly set the returning value result:=1;. BTW, cleaning the stack by lua_pop is optional. — Egor Skriptunoff
– Egor Skriptunoff, Commented May 12, 2013 at 22:46
Example of proper function declaration: function getsetting(L: Plua_State): Integer; cdecl; — Egor Skriptunoff
– Egor Skriptunoff, Commented May 12, 2013 at 22:49
I've done the following: -Changed return type from TLuaState to Integer. -Changed result value to 1. -Also I have deleted the lua_pop as you said It is working now just like that, but it didn't work with the "cdecl" in the function. Why is it needed? And about the "lua_CFunction", why do we need this if I can actually print the value like "print(getsetting(...))"? Thanks for the help. — user2308704
– user2308704, Commented May 13, 2013 at 11:48
Only functions conformed to lua_CFunction are possible to be available from Lua code. Please show your code where you are registering your function TLuaScripter.getsetting. — Egor Skriptunoff
– Egor Skriptunoff, Commented May 13, 2013 at 14:19
no problem, it's okay since now it's working properly. A lot of thanks! — user2308704
– user2308704, Commented May 13, 2013 at 14:58

user2308704 · Accepted Answer · 2013-06-17 01:57:31Z

It will work perfect with this. We have just added the result as integer and "result:=1"

function TLuaScripter.getsetting(LuaState: TLuaState): integer; var path,stri: string; i: integer; begin //getsetting('Targeting/TargetingEnabled') path := Lua_ToString(LuaState, 1); stri:= tree.GETsetting(path); lua_pushlstring(LuaState,Pansichar(ansistring(stri)),length(stri)); result:= 1; end;

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