attempt to compare string with number - computercraft - lua

Question

local level = 3 -- Required access level
local sideIn = "bottom" -- Keycard Input Side
local sideOut = "right" -- Redstone output side
local rsTime = 3 -- Redstone time
while true do
if disk.isPresent(sideIn) then
term.clear()
term.setCursorPos(1,1)
local code = fs.open("disk/passcode.lua", "r").readAll()
if code == nil then
local code = 0
else
local code = tonumber(code)
end
if code >= level then
print("> Access Granted")
disk.eject(sideIn)
rs.setOutput(sideOut,true)
sleep(rsTime)
rs.setOutput(sideOut,false)
else
print("> Permission Denied")
disk.eject(sideIn)
end
end
end
When there's no disk inserted, it throws an error:
.temp:15: attempt to compare string with number expected, got string
Does anyone know how to fix this issue? I throwed in a nil checker but it seems to not work. Any ideas on how could I fix this? I've been trying for at least half an hour now, and I still have no clue.

Answer 1

In this section:
local code = fs.open("disk/passcode.lua", "r").readAll() --(1)
if code == nil then
local code = 0 --(2)
else
local code = tonumber(code) --(3)
end
It first makes a new local variable with local code = .... In the new block that you create with the if, you also create new local variables with local code = .... Since it has the same name as the local before it, it "masks" it, prohibiting you from accessing the first code in the rest of the block. The value that you assign 0 to is not the same variable outside the if, so the first code is unaffected. At else the block for the second code ends and the same thing happens between else and end when the condition is false. To not assign the values 0 or tonumber(code) to new variables, you have to remove the local from local code = .... So the following is what it should be:
local level = 3 -- Required access level
local sideIn = "bottom" -- Keycard Input Side
local sideOut = "right" -- Redstone output side
local rsTime = 3 -- Redstone time
while true do
if disk.isPresent(sideIn) then
term.clear()
term.setCursorPos(1,1)
local code = fs.open("disk/passcode.lua", "r").readAll()
if code == nil then
code = 0
else
code = tonumber(code)
end
if code >= level then
print("> Access Granted")
disk.eject(sideIn)
rs.setOutput(sideOut,true)
sleep(rsTime)
rs.setOutput(sideOut,false)
else
print("> Permission Denied")
disk.eject(sideIn)
end
end
end