Distance finder not printing text - lua

Question

I'm trying to make this sign that, when you step close enough, shows a GUI.
To test it, I made it print("It works!") but It won't print anything.
LocalScript:
local Players = game:GetService('Players')
local LocalPlayer = Players.LocalPlayer
for _,Player in next, Players:GetChildren() do
local character = Player.Character
if character and character.Parent and Player ~= LocalPlayer then
local Magnitude = (LocalPlayer.Character.HumanoidRootPart.Position - character.HumanoidRootPart.Position).magnitude
end
end
while true do
if Magnitude < 10 then
print("It's working!")
end
end

Answer 1

The issue is that you have put a LocalScript into a Part in the Workspace. If you check the LocalScript docs, you'll see that ...
a LocalScript will only run Lua code if it is a descendant of one of the following objects:
A Player’s Backpack, such as a child of a Tool
A Player’s character model
A Player’s PlayerGui
A Player’s PlayerScripts.
The ReplicatedFirst service
So to fix your issue, you either need to
A) convert your code to a Script and access the Player objects through the Players service. or
B) move the LocalScript to a place where it will start executing and update the code accordingly.
If you go the route of Option B, follow these steps :
First, move the LocalScript into StarterPlayer > StarterCharacterScripts. This will cause the script to execute when the player's character spawns into the world.
Then, update the code so that it can find the block and show the distance to the player.
local localPlayer = game.Players.LocalPlayer
-- locate the sign in the world
-- local signGui = game.Workspace:WaitForChild("Part"):WaitForChild("UI")
-- set the range where the sign should appear
local DISTANCE_TO_SHOW_SIGN = 10 -- studs
-- every game tick, calculate the distance between the part and the character
game.RunService.Heartbeat:Connect(function()
-- escape if the player's character doesn't exist
if not localPlayer.Character then
return
end
-- calculate the distance to each of the players
-- if two players are close enough to each other, show the sign
local shouldShowSign = false
local myPosition = localPlayer.Character.HumanoidRootPart.Position
for _, otherPlayer in ipairs(game.Players:GetPlayers()) do
if (otherPlayer ~= localPlayer) and (otherPlayer.Character) then
local theirPosition = otherPlayer.Character.HumanoidRootPart.Position
local distBetween = (myPosition - theirPosition)
-- optimization : when calculating distance, try to avoid using square roots
-- use pythagorean theorem : dist = sqrt(x^2 + y^2 + z^2)
-- instead, use dist^2 = x^2 + y^2 + z^2
if (distBetween * distBetween) < (DISTANCE_TO_SHOW_SIGN ^ 2) then
shouldShowSign = true
break
end
end
end
-- show the sign if two players are close enough together
if shouldShowSign then
print("it's working")
end
-- optimization : only set the visibility when it changes
-- if signGui.Visible ~= shouldShowSign then
-- signGui.Visible = shouldShowSign
-- end
end)

Answer 2

Your code has 3 main issues
1: Its a regular script, not a localscript
2: Your while true do loop will timeout when the server starts
3: Magnitude is only defined when doing for i,v
Try this code in a localscript instead
local Players = game:GetService('Players')
local LocalPlayer = Players.LocalPlayer
local Magnitude
while true do
wait()
for _,Player in next, Players:GetChildren() do
local character = Player.Character
if character and character.Parent and Player ~= LocalPlayer then
Magnitude = (LocalPlayer.Character.HumanoidRootPart.Position - character.HumanoidRootPart.Position).magnitude
end
end
if Magnitude ~= nil then
if Magnitude < 10 then
print("It's working!")
end
end
end