Send Arguments to Callback?

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#1

I’m using BindAction and the second argument in that is a callback. BindAction sends the action’s name, userinputstate, and inputobject. Is there any way to send more arguments to the callback?

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#2

You could pass a function that calls the “real” callback with the parameters passed by BindAction plus some more parameters.

E.g.:


local ActionS = game:GetService("ContextActionService")

local function onFPressed(actionName, inputState, inputObject, aaaandAnotherOne, ...)
	print(aaaandAnotherOne)
	return Enum.ContextActionResult.Sink
end

ActionS:BindAction("actionName", function(an, is, io) return onFPressed(an, is, io, "test") end, false, Enum.KeyCode.F)

EDIT: You can do this a bit more elegantly with currying. It’s essentially creating a specialized version of a function where some of the parameters are decided before-hand, meaning you don’t have to call them with that parameter.

Here’s a function that curries a function:

local function curry(f, argN, argV)
	return function( ... )
		local args = {...}
		table.insert(args, argN, argV)
		return f(unpack(args))
	end
end

Here’s an example of how it can be used:

Without currying:

local function errorPrint(firstString, ...)
	print( script:GetFullName() .. " ERROR: " .. firstString, ... )
end

With currying:

local errorPrint = curry(print, 1, "ScriptName: " .. " ERROR: ")

In both cases, errorPrint("test print") would print (ScriptName: ERROR: test print)

And here’s how the stuff from before could be done with currying:

ActionS:BindAction("actionName", curry(onFPressed, 4, "testString"), false, Enum.KeyCode.F)
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#3

Could you point me to any resources where I could learn more in depth about currying, I have a use-case for it and I really wanna understand how it works but I’m still confused about it

#4

Hi, I’ve since learned that’s actually not currying but partial application, although the terms are often mixed up.

Here’s a decent explanation:

http://lua-users.org/wiki/CurriedLua

Wikipedia is also alright

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