Only one instance of a function running, and a new instance can be created at any time

[treebee63]

Hi,

I use this coding pattern a lot in my projects, but it’s really clunky to set up.
I’m wondering if there’s a better way to set it up.

Current pattern I have set up.

local jobID = 0
local function foo()
	--[[
	Requirements of this function:
		- only one instance of it should be running at any time
		- the function can be called at any time, usually it'll be called during its yield of task.wait() periods
		- if the function is already running and a new one is called, exit the old one
	--]]
	
	jobID = jobID + 1
	local currentJobID = jobID
	
	print("One", jobID)
	task.wait(1)
	if currentJobID ~= jobID then return end
	
	print("Two", jobID)
	task.wait(1)
	if currentJobID ~= jobID then return end
	
	print("Three", jobID)
end

for i = 1,10 do
	task.defer(function() 
		-- here we use task.defer, but in the real world case, foo() is usually called by multiple connected events
		foo()
	end)
	wait(0.25) -- we call the function faster than it's able to complete itself
end

Required Output:

  One 1
  One 2
  One 3
  One 4
  One 5
  One 6
  One 7
  One 8
  One 9
  One 10
  Two 10
  Three 10

[treebee63]

Ok, closure on this. This can be achieved by using task.cancel().

local function fooReal(i)
	print("One", i)
	task.wait(1)

	print("Two", i)
	task.wait(1)

	print("Three", i)
end

local activeFoo
local function foo(...)
	--[[
	Requirements of this function:
		- only one instance of it should be running at any time
		- the function can be called at any time, usually it'll be called during its yield of task.wait() periods
		- if the function is already running and a new one is called, exit the old one
	--]]
	
	if activeFoo then
		task.cancel(activeFoo)
		activeFoo = nil
	end
	
	activeFoo = task.spawn(fooReal, ...)
end

for i = 1,10 do
	task.defer(function() 
		-- here we use task.defer, but in the real world case, foo() is usually called by multiple connected events
		foo(i)
	end)
	wait(0.25) -- we call the function faster than it's able to complete itself
end