Re: Howto set global variable as ReadOnly

[Peter Shook <pshook@...>]

Jean Claude Morlier wrote:
> I want to export some variable (userdata, function, string,...)
> from C++ to LuaState.
> How can I do to set this variables ReadOnly.

If you want to make all globals readonly, see lua-5.0/test/readonly.lua

If you want to make only a few variables readonly, try something like this:

$ cat ro.lua
-- make some global variables readonly

local ReadOnly = {
  x = 5,
  y = 'bob',
}

local function check(tab, name, value)
  if rawget(ReadOnly, name) then
    error(name ..' is a read only variable', 2)
  end
  rawset(tab, name, value)
end

setmetatable(_G, {__index=ReadOnly, __newindex=check})


$ lua -i ro.lua
> = x
5
> = y
bob
> z = 'junk'
> x = 4
stdin:1: x is a read only variable
stack traceback:
        [C]: in function `error'
        ro.lua:11: in function <ro.lua:9>
        stdin:1: in main chunk
        [C]: ?
> = x
5
> = z
junk
>

- Peter Shook