class binding question

["W. Scott Dillman" <sdillman@...>]

 

 

I have a pretty noob question but I have several ways to solve my problem and I think I just
need a nudge in the right direction.

 

I found Virgil Smith's post here: http://lua-users.org/lists/lua-l/2003-12/msg00483.html

 

That describes in detail what I am trying to do, but I must be missing something.

 

Here is what I am trying to do ( pretty common ), I know I can use all the binding libraries
and add-ons out there, but I prefer to write my own.

 

Lets say I have a C++ class like the following:

 

class A
{
public:
A() : iSomeVal(0){}
int iSomeVal;
int doSomething(int i);
}

 

And I want to be able to do this in lua:

 

A("myA");

 

myA.iSomeVal = 10;

 

local x = myA.iSomeVal;

 

myA:doSomething(x);

 

I can get pieces of the above to work, but I am missing something somewhere.

 

If I use a method table to register my object and methods, something like this:

 

lua_pushliteral(L, "__index");
lua_pushvalue(L, methodtable);
lua_settable(L, metatable);

 

Where methodtable is a table filled with cfunctions and upvalues something like:

 

myA:doSomething(x)

 

works great, but I am at a loss at how to implement the reading of member data
because something like:

 

local x = myA.iSomeVal;

 

returns whatever is in the table field, so if I store it as a fuction; x now holds a function
reference, so I'm unsure how to implement it. Of course if I call:

 

local x = myA.iSomeVal();

 

It works, but is messy.

 

If I take the other route and do something like:

 

lua_pushliteral(L, "__index");
lua_pushcfunction(L, &myGetter);
lua_settable(L, metatable);

 

And do my decision making about function or member in the 'myGetter' function, it works
well but lua throws an error after the execution of the statement, if I call a function
complaining of a nil value, even though it executes fine.

 

Any advice would be great...

 

Thanks,
Scott