using Delphi classes in lua :)

[paul_nicholls]

Thanks much, Paul.

Quick question since I only skimmed your code. Does this, or can this, emulate properties too? And functions with variables, not just a single function with no variables or returns?

The only way I can think to simulate properties, is to create Get/Set methods in the TLuaClass descendent and use those :-)

To your other question, your TLuaClass methods MUST take 1 input parameter of type lua_State and return a result as Integer like so:

Function MyMethodName(L: lua_State): Integer;

but they can then quite happily receive any number of Lua input parameters via the lua_State's stack, and return any number of Lua variables back onto the lua_State's stack like so:

This one takes no input parameters and returns no results

Function  TLuaClassCounter.IncCount(L: lua_State): Integer;
Begin
    Inc(FCount);

    Result := 0;
End;

This one takes no input parameters and returns 1 result (the number)

Function  TLuaClassCounter.GetCount(L: lua_State): Integer; 
Begin
    lua_pushnumber(L,FCount);

    Result := 1;
End;

Here is an example of a TLuaClass method that takes 2 numbers, and returns the Sum and the Difference of the 2 numbers as 2 separate results

Function TLuaClassTest.SumDiff(L: lua_State): Integer;
Var
    a,b: Single;
    sum,diff: Single;
Begin
    //  make sure that there are 2 inputs, and that they are numbers
    a := luaL_checknumber(L,1);
    b := luaL_checknumber(L,2);

    sum := a + b;
    diff := a - b;

    //  push both results onto the Lua stack
    lua_pushnumber(L,sum);
    lua_pushnumber(L,diff);

    Result := 2;
End;

For example this may be called like so in a Lua script:

a,b = Test.SumDiff(5,10) -- assume it is created already

print(a,b)

This one calles the appropriate internal TLuaClass methods depending on the MethodIndex

Function  TLuaClassCounter.CallLuaMethod(L: lua_State; MethodIndex: Integer): Integer;
Begin
    Case MethodIndex Of
        0 : Result := IncCount(L);
        1 : Result := GetCount(L);
    Else
        lua_pushstring(L,PChar(Format(
            'TLuaClassCounter.CallLuaMethod: MethodIndex "%d" out of bounds',
            [MethodIndex])));
        lua_error(L);
    End;
End;