How to substitute an exposed vehicle controller function?

So here's my problem. I've made a jbeam part that uses a custom controller with the path: \lua\vehicle\controller\. Inside the controller file there's a line of code:

Code:

M.update = nop

When I try to substitute this function like this:

Code:

local function updateModified(dt)
  print("hi")
end
M.update = updateModified

or like this:

Code:

controller.getControllerSafe("controllerName").update = function(dt) print("hi") end

, nothing happens. The first way works for other lua modules though.
Am I missing something? Any help appreciated!

 

Quick update. Probably I'll just use boolean flags and if-statements.

By the way, I've also found another workaround to the problem:

Code:

local function testFunction(dt)
  print("hi")
end

local function update(dt)
  M.intermediateFunction(dt)
end

M.update = update
M.intermediateFunction = nop

After running

Code:

M.intermediateFunction = testFunction

the module starts printing the word.