Re: __index function in a metatable shared by several tables

[Ignacio Burgueño <ignaciob@...>]

Tim Hunter wrote:
> Sorry for the vague subject. I don't know better words to summarize my 
> question.
>
> The following code prints
> 1
> You called foo
>
> Is there any way for the function f to modify o.test? In my code there 
> could be multiple o tables, all sharing the t metatable. I would like 
> function f to store state information in each individual o table.
>
>
> t = {}
>
> setmetatable(t, {__index =
>   function(_, k)
>     local function f()
>       print("You called " .. k)
>     end
>     return f
>   end
> })
>
> o = setmetatable({ test=1 }, t)
> t.__index = t
>
> print(o.test)
> o.foo()


Will this work for you?

mt = {
  __index = function(tab, k)
    local function f()
      print("You called " .. k .." on "..tostring(tab))
      tab.test = 20 * math.random()
    end
    return f
  end
}

o = setmetatable({ test=1 }, mt)
o2 = setmetatable({ test=1 }, mt)

print(o.test)
o.foo()
print(o.test)

print(o2.test)
o2.foo()
print(o2.test)

assert(o2.test ~= o.test)