I’m trying to compare a number plate found in a SQL database to a vehicle in the open world. If I manage to get a positive match, everything is fine, however if I get a failed match (as the SQL result gives a nil result since it cannot find the number plate from in-game in the database), the script breaks and gives me the error:
attempt to index a nil value (field '?')
How do I deal with receiving a nil result? Example code:
if carPlate == databasePlate then
– DO CODE
else
– DO SOME OTHER CODE
end
The script will do “SOME CODE” if the plates match but will kill the script in error rather than doing “DO SOME OTHER CODE”.
I apologize if this doesn’t make much sense as I’m quiet new to LUA programming but I thank you in advance for any help with this.
You are trying to concat a string, that only works with tables
local argString = table.concat(plate, " ")
And it looks like your not even using that for anything, Heres something I wipped up that should do what you want it todo (with prints for debugging).
RegisterServerEvent('Vehicles:Impound:clientPlateCheck')
AddEventHandler('Vehicles:Impound:clientPlateCheck', function(plate)
if plate == nil then print("Error plate is nil.") TriggerClientEvent('esx:showNotification', source, '~g~ Plate sent from client is nil.') return end
MySQL.Async.fetchAll('SELECT plate FROM h_impounded_vehicles WHERE plate = @plate', {
['@plate'] = plate
}, function(result)
print("Dumping result table.")
print(ESX.DumpTable(result))
if result[1].plate == plate then
print("Match found, Triggering client event back to source.")
TriggerClientEvent('esx:showNotification', source, '~g~ Plate matches.')
else
print("Match not found, Triggering client event back to source.")
TriggerClientEvent('esx:showNotification', source, '~r~ No match found.')
end
end)
end)
If I directly copy and paste your code, I receive the error: server.lua:38: attempt to index a nil value (global 'ESX')
So I commented out the following: --print(ESX.DumpTable(result))
Then I get the following error: SCRIPT ERROR: Execution of native 000000002f7a49e6 in script host failed: Argument at index 1 was null.
Now for some reason when getting the number plate from the closet vehicle, it adds an extra space at the end of the result (from previous testing). Example: 'JQP 043 '
So I added the following to remove the last character: plate = plate:sub(1, -2)
But now I get the error: SCRIPT ERROR: Execution of native 000000002f7a49e6 in script host failed: Argument at index 1 was null.
I didn’t think trying to compare a physical vehicle in front of the player ped and to a vehicle stored in the database table was going to be this difficult haha. I appreciate the help - hopefully this gets solved
RegisterServerEvent('HRP:Impound:clientPlateCheck')
AddEventHandler('HRP:Impound:clientPlateCheck', function(plate)
if plate == nil then
print("Error plate is nil.")
TriggerClientEvent('esx:showNotification', '~g~ Plate sent from client is nil.')
return
end
plate = plate:sub(1, -2)
MySQL.Async.fetchAll('SELECT plate FROM h_impounded_vehicles WHERE plate = @plate', {
['@plate'] = plate
}, function(result)
print("Dumping result table.")
print(_ESX.DumpTable(result))
if result[1].plate == plate then
print("Match found, Triggering client event back to source.")
TriggerClientEvent('esx:showNotification', '~g~ Plate matches.')
else
print("Match not found, Triggering client event back to source.")
TriggerClientEvent('esx:showNotification', '~r~ No match found.')
end
end)
end)
Hey what is on line 43? in the server.lua it seems to be a nil value
EDIT: You can also try this, I dont really know if this is the issue since i dont know whats on line 43 yet but feel free to drop this in instead
MySQL.Async.fetchAll('SELECT plate FROM h_impounded_vehicles WHERE plate = @plate', {
['@plate'] = plate
}, function(result)
print("Dumping result table.")
print(_ESX.DumpTable(result))
if result[1].plate then
print("Match found, Triggering client event back to source.")
TriggerClientEvent('esx:showNotification', '~g~ Plate matches.')
else
print("Match not found, Triggering client event back to source.")
TriggerClientEvent('esx:showNotification', '~r~ No match found.')
end
end)
The way this works is simple, It will check if there is a plate key in the table from msql and if there is it should be the same as the one passed over since you are fetching it with the desired license plate, I believe this is the issue as to why it drops a error when you dont get a plate stored in the database.
Every method I’ve tried works when retrieving the confirmed plate however I’d like to display an error message (using notifications) to the player when there is no match.
[script:hrp_pd_impoun] Dumping result table.
[script:hrp_pd_impoun] {
[script:hrp_pd_impoun] }
[script:hrp_pd_impoun] SCRIPT ERROR: @hrp_pd_impound/server.lua:43: attempt to index a nil value (field '?')
[script:hrp_pd_impoun] > <unknown> (@mysql-async/mysql-async.js:15543)
[ script:mysql-async]
I’ve spent over 15 hours (and I wish I was lying) using Google to try solve this issue whilst trying many methods but just can’t seem to find a way to deal with a nil result.
Also, if I have any TriggerClientEvent’s in the function(result) block, I get the following error:
[ c-scripting-core] InvokeNative: execution failed: Argument at index 1 was null.
[script:hrp_pd_impoun] SCRIPT ERROR: Execution of native 000000002f7a49e6 in script host failed: Argument at index 1 was null.
[script:hrp_pd_impoun] > <unknown> (@mysql-async/mysql-async.js:15543)
And we’ve cracked it - I really appreciate your help throughout this. The debugging print was the biggest help, which for some odd reason I just never thought of doing. Here is the code used below for anyone who may come across this on Google.
RegisterServerEvent('HRP:Impound:clientPlateCheck')
AddEventHandler('HRP:Impound:clientPlateCheck', function(plate)
_source = source;
if plate == nil then
print("ERROR: No plate received")
TriggerClientEvent('esx:showNotification', source, '~r~ERROR: ~s~You need to be facing a vehicle')
return
else
print('Plate Retrieved: ' .. plate)
end
plate = plate:sub(1, -2)
MySQL.Async.fetchAll('SELECT plate FROM h_impounded_vehicles WHERE plate = @plate', {
['@plate'] = plate
}, function(result)
print("Table Result:")
print(_ESX.DumpTable(result))
if not next(result) then
print('Fail: No Match & ' .. plate)
TriggerClientEvent('esx:showNotification', _source, '~r~Failed')
else
print('Success: ' .. result[1].plate .. ' & ' .. plate)
TriggerClientEvent('esx:showNotification', _source, '~g~Success')
end
end)
end)
