ERROR: attempt to index a nil value

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CloudyYard
Prole
Posts: 12
Joined: Fri Jul 03, 2015 8:54 pm

ERROR: attempt to index a nil value

Post by CloudyYard »

Hello everyone!,
i have a problem...

i created a game minecraft-like but when I click on the edge of the world it's an error: attempt to index a nil value

code:

Code: Select all

function love.load()
	map = {}
	inv = {}
	
	size = 16
	maxStack = 64
	selected = 0
	invLen = 8
	
	ver = "1.0"
	id = ""
	
	mx = 0
	my = 0
	
	w = math.floor(768 / size)
	h = math.floor(576 / size)
	
	love.window.setMode(768, 576)
	love.window.setTitle("Cube2D "..ver)
	
	isblock = true
	
	image = 0
	stack = 1
	
	--blocks
	air = {}
	air[image] = love.graphics.newImage("assets/blocks/air.png")
	air[stack] = 0
	air[id] = "air"
	air[isblock] = false
	
	grass = {}
	grass[image] = love.graphics.newImage("assets/blocks/grass.png")
	grass[stack] = 0
	grass[id] = "grass"
	grass[isblock] = true
	
	dirt = {}
	dirt[image] = love.graphics.newImage("assets/blocks/dirt.png")
	dirt[stack] = 0
	dirt[id] = "dirt"
	dirt[isblock] = true
	
	stone = {}
	stone[image] = love.graphics.newImage("assets/blocks/stone.png")
	stone[stack] = 0
	stone[id] = "stone"
	stone[isblock] = true
	
	bedrock = {}
	bedrock[image] = love.graphics.newImage("assets/blocks/bedrock.png")
	bedrock[stack] = 0
	bedrock[id] = "bedrock"
	bedrock[isblock] = true
	
	cactus = {}
	cactus[image] = love.graphics.newImage("assets/blocks/cactus.png")
	cactus[stack] = 0
	cactus[id] = "cactus"
	cactus[isblock] = true
	
	trunck = {}
	trunck[image] = love.graphics.newImage("assets/blocks/trunck.png")
	trunck[stack] = 0
	trunck[id] = "trunck"
	trunck[isblock] = true
	
	leaves = {}
	leaves[image] = love.graphics.newImage("assets/blocks/leaves.png")
	leaves[stack] = 0
	leaves[id] = "leaves"
	leaves[isblock] = true
	
	sapling = {}
	sapling[image] = love.graphics.newImage("assets/blocks/sapling.png")
	sapling[stack] = 0
	sapling[id] = "sapling"
	sapling[isblock] = false
	
	--items
	pickaxe = {}
	pickaxe[image] = love.graphics.newImage("assets/items/pickaxe.png")
	pickaxe[stack] = 0
	pickaxe[id] = "pickaxe"
	pickaxe[isblock] = false
	
	generateLevel()
	newInv()
	
	inv[0] = stone
	inv[1] = sapling
	
	inv[0][stack] = 2
	inv[1][stack] = 2
	mod_init()
end

function addItem(item)
	for i=0, invLen do
		if inv[i][image] == item[image] then
			inv[i][stack] = inv[i][stack] + 1
			return
		end
	end
	for i = 0, invLen do
		if inv[i][image] == air[image] then
			inv[i] = item
			inv[i][stack] = inv[i][stack] + 1
			return
		end
	end
end

function newInv()
	for i = 0, invLen do
		inv[i] = air
	end
end

function generateLevel()
	for x = 0, w do
		map[x] = {}
		for y = 0, h do
			map[x][y] = air
		end
	end
	for x = 0, w do
		for y = 0, h do
			
		end
	end
	
	for x = 0, w do
		for y = 0, h do
			if map[x][y] ~= bedrock then
		      if y > 16 then
		      	map[x][y] = dirt
		      end
		   	if map[x][y] == dirt and map[x][y-1] == air then
					map[x][y-math.random(0, 1)] = grass
				end
				if map[x][y] == grass and map[x][y-1] ~= air then
					map[x][y] = dirt
				end
         end
		end
	end
	for x = 0, w do
		for y = 0, h do
			if map[x][y] == grass then
				map[x][y+4] = stone
			end
			if map[x][y] == stone then
				if map[x][y] ~= bedrock then
					map[x][y+1] = stone
				end
			end
		end
	end
	for x = 0, w do
		for y = 0, h do
			if math.random(0, 20) == 5 and map[x][y] == grass then
				map[x][y] = sapling
			end
		end
	end
end

function love.update(dt)
	mx, my = love.mouse.getPosition()
	mx = (math.ceil(mx / size) - 1)
	my = (math.ceil(my / size) - 1)

	if love.mouse.isDown("l") and map[mx][my] ~= air then
		if map[mx][my] == leaves then
			addItem(sapling)
		end
		addItem(map[mx][my])
		map[mx][my] = air
	end
	if love.mouse.isDown("r") and isblock then
		if map[mx][my] == air then
			map[mx][my] = inv[selected]
			map[mx][my][stack] = map[mx][my][stack] - 1
		end
	end
	mod_update()
end

function love.draw()
	mx, my = love.mouse.getPosition()
	mx = (math.ceil(mx / size) - 1)
	my = (math.ceil(my / size) - 1)
	
	love.graphics.setBackgroundColor(0, 50, 255)
	
	for x = 0, w do
		for y = 0, h do
			love.graphics.draw(map[x][y][image], x * size, y * size)
			
			if map[x][y] == dirt and map[x][y-1] == air then
				if math.random(0, 20) == 10 then
					map[x][y] = grass
				end
			end
			if map[x][y] == grass and map[x][y-1] ~= air and map[x][y-1] ~= flowers then
				map[x][y] = dirt
			end
		end
	end
	love.graphics.setColor(255,255,255,60)
	love.graphics.rectangle('fill', mx * size, my * size, size, size)
	love.graphics.setColor(255,255,255)
		
	for i=0, invLen do
		if inv[i][stack] <= 0 then
			inv[i] = air
		end
		
		love.graphics.setColor(0,50,255)
		love.graphics.rectangle("line", (selected*34)+37, 549, 19, 20)
		love.graphics.setColor(0,50,100)
		love.graphics.rectangle("fill", (i*34)+38, 550, 18, 18)
		love.graphics.setColor(255, 255, 255)
		
		love.graphics.draw(inv[i][image], (i*34)+39, 551)
		love.graphics.setColor(255, 255, 255)
		
		if inv[i][stack] > 1 then
			love.graphics.setColor(0, 0, 0)
			love.graphics.print(inv[i][stack], (i*34)+38, 536)
			love.graphics.setColor(255, 255, 255)
		end
	end
	
	for x = 0, w do
		for y = 0, h do
			if map[x][y] == sapling and math.random(0, 100) == 5 then
				map[x][y] = trunck
				map[x][y-1] = trunck
				map[x][y-2] = trunck
				map[x][y-3] = trunck
				map[x][y-4] = trunck
				map[x][y-5] = trunck
				map[x][y-6] = trunck
				map[x-1][y-4] = leaves
				map[x+1][y-4] = leaves
				map[x-1][y-5] = leaves
				map[x+1][y-5] = leaves
				map[x-1][y-6] = leaves
				map[x+1][y-6] = leaves
				map[x][y-7] = leaves
				map[x+2][y-5] = leaves
				map[x-2][y-5] = leaves
			end
		end
	end
	mod_draw()
end

function love.keypressed(key)
	if key == "1" then
		selected = 0
	elseif key == "2" then
		selected = 1
	elseif key == "3" then
		selected = 2
	elseif key == "4" then
		selected = 3
	elseif key == "5" then
		selected = 4
	elseif key == "6" then
		selected = 5
	elseif key == "7" then
		selected = 6
	elseif key == "8" then
		selected = 7
	elseif key == "9" then
		selected = 8
	end
end
photo:
Image

error:

Code: Select all

Error: main.lua:178: attempt to index a nil value
stack traceback:
	main.lua:178: in function 'update'
	[string "boot.lua"]:442: in function <[string "boot.lua"]:413>
	[C]: in function 'xpcall'
Help me please!!
Joe Black
Prole
Posts: 39
Joined: Wed Jan 21, 2015 1:57 pm

Re: ERROR: attempt to index a nil value

Post by Joe Black »

hello,

when mouse X coordinate is 0 you got mx = -1 (after math..) so it failed

you can modify the computation line 174-175 to :

Code: Select all

   mx = (math.floor(mx / size))
   my = (math.floor(my / size))
it looks it works
CloudyYard
Prole
Posts: 12
Joined: Fri Jul 03, 2015 8:54 pm

Re: ERROR: attempt to index a nil value

Post by CloudyYard »

Thank you! now it is working perfectly!
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