SWIG/Lua/C++ object instance

[Joey Mukherjee <joey@...>]

I create an instance of my class variable in C++ and want to use Lua  
to use some of the routines in my C++ class so I used SWIG to  
generate the bindings for Lua and I think I have that right.

However, I can not figure out how to make Lua use my C++ variable  
instance instead of creating a new one.  I was looking at the Wiki  
and I am very close to the CppObjectBinding method, except I am using  
SWIG.

I have a :

    lua_pushlightuserdata (global_Lua_state, this);
    lua_setglobal (global_Lua_state, "this");

to put the "this" pointer on the stack.  I want to interface that  
with Lua:


print ("In the Lua script")
b = plot.Plot(this)  -- wrong!  How do I make b = this, but be of a  
plot.Plot () type.
print (this)
print (b)
print (b:DumpV (0))
print (this:DumpV(0))

Two addresses are printed out, but they are different (which I  
expect).  I want to do this:DumpV (0), but I get a:

In the Lua script
userdata: bc4dd8
userdata: b53330
dump.lua:7: attempt to index global 'this' (a userdata value)

I feel I am missing something simple, but I just can't get the next  
step.  I feel like if I go to the direct way of binding like in the  
wiki CppObjectBinding, I can get this to work, but then I have to do  
all the bindings myself so I would like to stick with SWIG.

Thanks for any ideas!

Joey