CODEWITHSUNDEEP
lua
Joel
Joel

Reputation: 17

Lua: attempt to perform arithmetic on global 'mapfinishes' (a nil value)

I'm trying to set up something in a game that runs off of Lua and this specific local function is triggered when the player finishes the map. Here is the code:

local function setDrRanks( ply )
    local name = SQLStr( ply:Nick() )
    local sid = ply:SteamID()

    drsql:query( "SELECT MapFinishes from dr_exp WHERE SteamID = '"..sid.."'", function( q, data )
        local row = data[1]

        if ( row ) then
            mapfinishes = row["Mapfinishes"]
        end

        drsql:query( "REPLACE into dr_exp (`SteamID`, `PlayerName`, `MapFinishes`) VALUES('"..sid.."', "..name..", '"..(mapfinishes+1).."');" );
    end )
end

The function is to insert into SQL via a lua function, which it did successfully when ran the first time, as the player was at 0 finishes. Once they hit 1, it refused to do a simple +1 on the mapfinishes value. Which strange is that this seems to work 100% when the player is at 0 finishes, and it will put them at 1, but once they are at 1, it will not add to it any longer. The error received is:

attempt to perform arithmetic on global 'mapfinishes' (a nil value)

Anyone have any ideas? Thanks in advance.

Upvotes: 0

Views: 16489

Answers (1)

legends2k
legends2k

Reputation: 32954

    local row = data[1]

    if ( row ) then
        mapfinishes = row["Mapfinishes"]
    end

    drsql:query( "REPLACE into dr_exp (`SteamID`, `PlayerName`, `MapFinishes`) VALUES('"..sid.."', "..name..", '"..(mapfinishes+1).."');" )

The issue is in the expression mapfinishes+1 which seems to have gotten executed without mapfinishes getting set. This implies that the if loop above didn't execute because row was nil or false. Remember, in Lua, zero and the empty string are truth values.

Another possibility is that the row["Mapfinishes"] itself was nil so that mapfinishes remains nil.

Usually it's better to have minimal/no global variables. If you're going to use mapfinishes only within this function, it'd be appropriate to declare it local.

Upvotes: 1

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