Using exports with function as a parameter/callback

[chris1384]

It's going to be hard to explain so bear with me.

Supposed we have a function like this (function is in a string):

exports.myresource:addProperty("security", "function(player) return getPlayerName(player) == 'owner' end")

Then, in myresource the string is then put in a loadstring function, as following (it only checks it, doesn't add it anywhere):

local testPlayer = getPlayerFromName("player1") -- testing purposes
local loadstringed = loadstring(name.. " = ".. func_str)
local success, info = pcall(loadstringed, testPlayer)

iprint(success, info)
-- outputs:
true, nil

Apparently everything seems to work, the function does indeed exist, but doesn't seem to take any parameters into it.

How do you make a function loaded with loadstring() that also supports parameters?
 

Edited April 12, 2023 by chris1384

[IIYAMA]

52 minutes ago, chris1384 said:

How do you make a function loaded with loadstring() that also supports parameters?

 

When loading code, you are putting a kind of chunk/function around it.

So basically this:

function(player) return getPlayerName(player) == 'owner' end

Looks more or less like this:

 --  pcall(loadstringed) is calling this chunk/function:
function ()
	function(player) return getPlayerName(player) == 'owner' end
end

 

So in order to solve this:

return function(player) return getPlayerName(player) == 'owner' end

 

local success, theFunc = pcall(loadstringed)

local success2, isOwner = pcall(theFunc, testPlayer)

 

See also xpcall for better error handling:

https://www.gammon.com.au/scripts/doc.php?lua=xpcall

[P[ow]er]

local func_str = "function(player) return getPlayerName(player) == owner end"
local loadstringed = loadstring("local owner = 'owner'; return function(player) "..func_str.." end")
local myFunc = loadstringed()

-- Call the function with a parameter
local testPlayer = getPlayerFromName("player1")
local result = myFunc(testPlayer)
print(result) -- true

---

local func_str = "function(player) return getPlayerName(player) == 'owner' end"
local loadstringed = loadstring("return "..func_str)
local success, myFunc = pcall(loadstringed)

-- Call the function with a parameter
local testPlayer = getPlayerFromName("player1")
local success2, isOwner = pcall(myFunc, testPlayer)

print(success2, isOwner) -- true    false

 

[DiSaMe]

The proper way in Lua to use arguments in a function created using loadstring is vararg expression, written as three dots.

local argument1, argument2, argument3 = ...

In your case, the function body would look like this:

local player = ...
return getPlayerName(player) == 'owner'

An example with loadstring:

local func_str = "local player = ... return getPlayerName(player) == 'owner'"
local loadstringed = loadstring(func_str)
local testPlayer = getPlayerFromName("player1")
local success, info = pcall(loadstringed, testPlayer)

[chris1384]

Everything is working now. It was easier than I thought lol.

11 hours ago, DiSaMe said:

The proper way in Lua to use arguments in a function created using loadstring is vararg expression, written as three dots.

local argument1, argument2, argument3 = ...

In your case, the function body would look like this:

local player = ...
return getPlayerName(player) == 'owner'

An example with loadstring:

local func_str = "local player = ... return getPlayerName(player) == 'owner'"
local loadstringed = loadstring(func_str)
local testPlayer = getPlayerFromName("player1")
local success, info = pcall(loadstringed, testPlayer)

I was planning to use this in the future, I had to get over the basics first because that's where it screwed me up the most. Thanks for the tip

And thank you all for helping!