Re: Linking values to lua with set/get
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- Subject: Re: Linking values to lua with set/get
- From: Sam Roberts <sroberts@...>
- Date: Thu, 1 Mar 2007 09:46:28 -0800
On Thu, Mar 01, 2007 at 12:11:05PM +0100, Timm Felden wrote:
> Is there a way of writing a function "lua_link( name, set, get );", that
> would do this:
> lua: name = <any value(s)>
> -> invokes the parameter passed as set, this is like the normal C-functions
>
> lua: x = name
> -> invokes set, which is also a normal C-function, but by default gets
> no parameters and returns only one.
>
> I ask, because I have to take care of values between lua and C and atm
> I'm using functions, what is pretty ugly:P
Doing
name = 4
is the same as
getfenv()['name'] = 4
Lua 5.1.1 Copyright (C) 1994-2006 Lua.org, PUC-Rio
> = getfenv()['hi']
nil
> getfenv()['hi'] = 3
> = getfenv()['hi']
3
> = hi
3
so you can make a metatable for your function environment (the table
returned by getfenv()), and define __index and __newindex in that
metatable to do your linking.
Is something like this what you are thinking of? Its written in lua, but
you can do the same thing in C, or just call attr_link() from C:
function attr_setup()
-- handlers: name => { fn get, fn set }
local handlers = {}
local mt = {
__index = function(t, k)
local h = handlers[k]
return h and h.get()
end,
__newindex = function(t, k, v)
local h = handlers[k]
if h then
return h.set(v)
else
rawset(t, k, v)
end
end,
}
setmetatable(getfenv(), mt)
function attr_link(name, set, get)
handlers[name] = { set = set, get = get }
end
end
attr_setup()
do
local v_ = 3
attr_link('fu', function(v) v_ = v end, function() return v_ end)
end
fu = fu + 1
bar = fu
print(bar)