Type checking optional callback

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1

I have an optional callback function, is the following format correct?

callback: (() -> ())?

It appears slightly differently compared to when it is callback: () -> () which is why I want to make sure.

2

This means that the function can be nil (that is not exist), () -> () indicates that the function always exists.

It is useful if sometimes the function is not established or when the property of the table begins as nil.

What changes are there with this? This warning will appear

image
image446×149 4.91 KB

How is it solved? Adding an if.

type F = () -> ()?

local myFunction: F = nil :: any
if myFunction then
	myFunction()
end

If there is no If and the function is still nil, there will be an error.

attempt to call a nil value

3

Thanks for the reply, but I am already aware that you need to check if the function exists before calling it. My question is whether the syntax func: (() -> ())? is correct to make func optional (could be nil).

You wrote this here, is this the correct syntax? This does not seem to be right because I get an error.
image

4

Honestly makes sense to give that type to a function that is already defined in the variable.

But well, the correct way is so:

local Something = function()
	
end :: () -> ()?

or

local Something: () -> ()? = function()
	
end