Attempt to index field '?' a nil value error

Solar2D Lua Language
#1

I am working on a jumper game to practice my lua programming and I have come across a problem.  I created a function to determine what will happen when the character is hit by an enemy. However, it gives me an “Attempt to index field ‘?’ a nil value” error pointing to Line 269. This only happens if the enemy is hit at a certain point on its body, and I am not sure why. Otherwise, it works fine.

local function playerHit()

        character.x = _L + 250

        character.alpha = 1

        lives[livesCount].alpha = 0 --Line 269

        livesCount = livesCount - 1

        if(livesCount <= 0) then

            onGameOver()

        end

    end

I think it might be referring to lives[livesCount] as nil, but I defined it in my forward declares and defined its graphics in a for loop way before this function:

– forward declarations and other locals

local lives = {} – table that will hold the lives object

local livesCount = 4 – the number of lives the player has

for i=1, livesCount do

        lives[i] = display.newImageRect(“heart.png”, 50, 50)

        lives[i].x = _L + (i * 65) - 25

        lives[i].y = _T + 50

    end

If anybody has a solution to this, it would be greatly appreciated.

#2 
local function playerHit() character.x = \_L + 250 character.alpha = 1 lives[livesCount].alpha = 0 --Line 269 livesCount = livesCount - 1 if(livesCount \<= 0) then onGameOver() end end

If livesCount is equal to 0 you’re going to try and access  lives[0] which doesn’t exist. You probably should be testing if livesCount < 1 then calling onGameOver().

Rob

#3

Thank you for your quick reply, but this is occurs when the user has all of their lives. Is it possible to split playerHit() in to two different functions, and run them both?

local function showPlayerHit()

            character.alpha = 0.5

            local tmr_onPlayerHit = timer.performWithDelay(1, playerHit, 1)

            --add second timer

        end

        

            if(event.object1.id == “enemy” and event.object2.id == “character”) then

                showPlayerHit()

                removeOnPlayerHit(event.object1, nil)

            end

        

            if(event.object1.id == “character” and event.object2.id == “enemy”) then

                showPlayerHit()

                removeOnPlayerHit(nil, event.object2)

            end

Thank you.

Sincerely,

Alex

#4

I would put a print statement before the line that errors out and find out what it thinks livesCount is. The error is basically saying that lives[livesCount] is not a table object. The most likely cause is that livesCount isn’t what you think it is and lives[livesCount] is nil

So finding out whats there is important.

Rob

#5 
local function playerHit() character.x = \_L + 250 character.alpha = 1 lives[livesCount].alpha = 0 --Line 269 livesCount = livesCount - 1 if(livesCount \<= 0) then onGameOver() end end

If livesCount is equal to 0 you’re going to try and access  lives[0] which doesn’t exist. You probably should be testing if livesCount < 1 then calling onGameOver().

Rob

#6

Thank you for your quick reply, but this is occurs when the user has all of their lives. Is it possible to split playerHit() in to two different functions, and run them both?

local function showPlayerHit()

            character.alpha = 0.5

            local tmr_onPlayerHit = timer.performWithDelay(1, playerHit, 1)

            --add second timer

        end

        

            if(event.object1.id == “enemy” and event.object2.id == “character”) then

                showPlayerHit()

                removeOnPlayerHit(event.object1, nil)

            end

        

            if(event.object1.id == “character” and event.object2.id == “enemy”) then

                showPlayerHit()

                removeOnPlayerHit(nil, event.object2)

            end

Thank you.

Sincerely,

Alex

#7

I would put a print statement before the line that errors out and find out what it thinks livesCount is. The error is basically saying that lives[livesCount] is not a table object. The most likely cause is that livesCount isn’t what you think it is and lives[livesCount] is nil

So finding out whats there is important.

Rob