What is a callback?

[sanafth]

I currently have been trying to understand certain things through the Documentation, but many of the pages mention “callbacks”

What exactly is a callback? What does it do? Is it important(

[JAcoboiskaka1121 (Skellyton)]

Its data that is supposed to be used by other data, heres a basic chart:

Here the main program calls a function, but in that function, calls another function, heres a basic code example:

function ReturnRandom()
return math.random(1, 20)
end

function GetResultAndMultiply(MultiplicationNum)
local ReturnedNum = ReturnRandom()
local Answer = ReturnedNum * MultiplicationNum

return Answer
end

function PrintAnswer()
local Answer = GetResultAndMultiply(5)

print(Answer)
end

PrintAnswer()

Here we have a 3 step process, we get a random number from the ReturnRandom function, The GetResultAndMultiply function gets that number and multiplies it, and then we call that function in the PrintAnswer function and print it.

This is just a basic example, and not the best, but that’s basically what a callback is, the GetResultAndMultiply and the ReturnRandom functions are the callback functions, heres a wikipedia explanation:

[sanafth]

I think I understand it a little better.

If I had a function and connected it to a remotevent that fires when a part is Touched, if i have that function call another function, that called function would be a callback?

In other words, a callback function is a function that is designed to be called by another function…
Nothing else?

[JAcoboiskaka1121 (Skellyton)]

@sanafth

In other words, a callback function is a function that is designed to be called by another function…
Nothing else?

Yep, that is correct.

the30isthelimit

[tlr22 (FusionOak)]

Yup. Furthermore all connections to events are callbacks. Since you are registering a function to be called when event happens.

[GE_0E]

I think that callback function are functions that are passed as an argument to other functions to get executed after a specific event (not 100% sure)

example

function functionExecuteRepeat(interval :number, func : () -> ())
	task.spawn(function()
		while true do
			func()
			
			task.wait(interval)
		end
	end)
end


local function print5()
	print(5)
end

functionExecuteRepeat(2, print5) -- print5 will get executed every 2 seconds

and you can also pass arguments to the passed callback function

function iterateTableOfNumbers(tbl : {number}, func : (number) -> ())
	for _, number in tbl do
		func(number) -- passes number as an argument to the function
	end
end

function printNumberPow2(num)
	print(num^2)
end

local tableOfNumbers = {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}

iterateTableOfNumbers(tableOfNumbers, printNumberPow2)

[sanafth]

Wow, that was suprisingly simple. Thanks for the help