How do I use a local GUI script run a function from another script when I press a button?

ModuleScripts!

ModuleScripts is a Lua source container, that is only ran once, and can only return one value.

-- ModuleScript

local module = {}

return module

How do we use these? I have a couple of examples:

-- ModuleScript

local myFunc = function() print("I am a function from a ModuleScript.") end;

return myFunc

-- The ModuleScript is placed in ReplicatedStorage, and it is named 'myModuleScript'.

The above code will return myFunc, which is a function that will print "I am a function from a ModuleScript." when it's called, defined as a variable. Now, to run this function from a Script (Same with LocalScripts).

-- Script

local repstore = game:GetService("ReplicatedStorage")
local myReturnedFunc = require(repstore:WaitForChild("myModuleScript"))

myReturnedFunc()

--[[ Expected Output

I am a function from a ModuleScript.
]]

To get the returned value from a ModuleScript, we use require. For more information about this, you can take a look at this link: https://www.robloxdev.com/articles/Built-in-Functions-and-Variables/Roblox

myReturnedFunc is the returned function which was contained in the ModuleScript (myModuleScript). And to call the function of course, we do myReturnedFunc().

The best thing about this, is that you can call this function from any Script/LocalScript aslong as the function is contained in a ModuleScript, and it is returned.

What if you want to use multiple functions in various scripts?

We use a table, and contain all the functions you want to call in it. There are two ways to put a function in a table:

-- ModuleScript

local myTable = {

myFunc = function()
print("I am a function inside a table.")
end;

myFuncTwo = function()
print("I am the second function inside the same table.")
end;
}

return myTable

or,

-- ModuleScript

local myTable = {}

function myTable.myFunc()
print("I am a function inside a table.")
end;

function myTable.myFuncTwo()
print("I am the second function inside the same table.")
end;

return myTable

How you call these functions are similar to the last way, except you need to get the functions from the returned table.

-- Script

local repstore = game:GetService("ReplicatedStorage")
local myReturnedTable = require(repstore:WaitForChild("myModuleScript")) -- This returns the table we made in the ModuleScript (myTable).

myReturnedTable.myFunc()
myReturnedTable.myFuncTwo()

--[[ Expected Output

I am a function inside a table.
I am the second function inside the same table.
]]

I hope I helped in any way, thanks for reading.

If you want to take a look at the wiki about this, here's the link: https://www.robloxdev.com/api-reference/class/ModuleScript