Question

The code says it all:

#tryModA.lua:
f,err=loadfile("tryModB.lua")
if not f then
    print("F is nil!!! Err:"..err)
else
    f.fn=function (x)
        print("x="..x)
    end
    f()
end

And here is the loaded file:

#tryModB.lua:
fn("hello")

Error:

lua: tryModA.lua:7: attempt to index global 'f' (a function value)
stack traceback:
    tryModA.lua:7: in main chunk
    [C]: ?

Question: why does it happen ?

Isn’t it true that loadfile() returns a function object and I can attach another function to it? PS. I come from a JavaScript programming background where it has prototype-based objects. I assume Lua has the same prototype based objects.

Answer 1

In Lua, loadfile() returns a function (not a function object) and functions can only be called. “Attaching” whatever to a function like you are trying is not possible.

Now, Lua tables are completely different story and the prototype-based concepts from JavaScript probably apply to them (I’m not very familiar with JS). The simplest way to make your code work at this point is to make fn global i.e. replace f.fn = function... with fn = function... although this might not be what you want.