Re: lua user data objects and interfacing c++

[Adrian Sietsma <adrian_groups@...>]

Robert Sadedin wrote:

> I am storing a c++ object in a lua user data, and binding a meta table 
> to it for lookup on method calls.
...
> What I would like to do is allow a user to add lua variables to these 
> c++ objects wrapped by a user data and accessed through the meta table.
>
> Currently a user can call, for instance:
> obj = createSomeObject()
> print(obj:getCVariable1())
>
> I'd like the user to be able to say:
> obj.x = 6
> print(obj.x)

you could try this :

1/ implement an upvalue attributes table in the metatable
2/ hook meta.__newindex() to add new attribs to the local table
3/ check attributes table first on meta.__index()

this would require a seperate metatble per userdata, but they can all 
share the __index and __newindex function

nb pairs will not see the attributes if you do this.

Adrian