Modules using each other's local objects

Question

In vanilla Lua 5.2, I have a module that contains:

Two local functions, A and B: B will always call A, A will sometimes call B and sometimes will call the functions stored in C;
C: a table (local). It contains tables which contains tables which can contain tables... which will at the end contain functions. These functions may call either A or B;
Then there's the return function, D, which will be returned when my module is loaded using require. It will call A.

At the end, it looks quite like this:

--don't pay attention to what the functions do:
--I am only writing them down to explain how they interact with each other

local A, B, C

C = {
    ...
    {
        function(a)
            B(a)
         end
    }
    ...
}

A = function(a)
    ...
    if (...) then
        B(a)
    end
    ...
    if (...) then
        C[...]...[...](a)
    end
    ...
end

B = function(a)
    A(a)
end

return function(s) -- we called this one D
    A(s)
end

Now, my problem is this: the declaration of C uses its own local variables, metatables and all that stuff, to the point I enclosed its declaration in a do ... end block.

It also is - with all those tables inside tables and newlines for each curly brace and indentation and so on - quite long. So I wanted to put it in its own module, but then it couldn't access B.

So, my question is: is there a way to pass B and maybe even A to the file where C is declared while loading it? I mean something like this, if it were possible:

--in the original module
local A, B, C

C = require("c", A, B)

...

And then, in c.lua:

local A, B = select(1, ...), select(2, ...)

C = {
    ...
    {
        function(a)
            B(a)
        end
    }
    ...
}

I really have no idea on how to do it.

Is there a way to pass variables from the requiring file to the required file which doesn't involve the variables being inserted in the global namespace?

score 3 · Accepted Answer · answered Aug 01 '16 at 17:48

main module:

local A, B, C

A = function(a)
    ...
    if (...) then
        B(a)
    end
    ...
    if (...) then
        C[...]...[...](a)
    end
    ...
end

B = function(a)
    A(a)
end

C = require("c")(A, B)

return function(s) -- we called this one D
    A(s)
end

c.lua:

local function C_constructor(A, B)
    local C = 
        {
            ...
            {
                function(a)
                    B(a)
                end
            }
            ...
        }
    return C
end

return C_constructor

That's clever, really clever. – user6245072 Aug 01 '16 at 18:29 — user6245072, Aug 01 '16 at 18:29

score 0 · Answer 2 · answered Aug 01 '16 at 15:09

0

Is there a way to pass variables from the requiring file to the required file which doesn't involve the variables being inserted in the global namespace?

Not with the default require function, but that shouldn't stop you from writing your own require function that does this. Obviously this will make the solution specific to your application, so those required files will not function correctly when a standard Lua interpreter (with its require function) is used.

answered Aug 01 '16 at 15:09

Paul Kulchenko

25,884
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That actually _will_ stop me lol. I'm not writing a standalone application actually, and I will one day traslate the whole codebase to C or C++, so why bother? – user6245072 Aug 01 '16 at 18:31

Modules using each other's local objects

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