LÖVE

Posted: **Wed Jun 07, 2023 6:51 pm**

I've been trying to learn LÖVE for a few days now and I decided to code snake for a first project. Sadly, I get an error this error when trying to draw the head.

Error
main.lua:80: bad argument #2 to 'rectangle' (number expected, got nil)

Traceback
[love "callbacks.lua"]:228: in function 'handler'
[C]: in function 'rectangle'
main.lua:80: in function 'draw'
[love "callbacks.lua"]:168: in function <[love "callbacks.lua"]:144>
[C]: in function 'xpcall'

Here's the code, (the line the error occurred has a comment)

Code: Select all

function love.load()
    love.window.setMode(700, 700)
    update = 0

    snake = {
        length = 1,
        speed = 4,

        facing = 0,

        bodyX = {0},
        bodyY = {0}
    }

    food = {
        x = love.math.random(1, 20) * 35,
        y = love.math.random(1, 20) * 35
    }

end

function love.update(dt)
    if love.keyboard.isDown("w", "up") then
        snake.facing = 1
    elseif love.keyboard.isDown("a", "left") then
        snake.facing = 2
    elseif love.keyboard.isDown("s", "down") then
        snake.facing = 3
    elseif love.keyboard.isDown("d", "right") then
        snake.facing = 4
    end

    if update == 0 then
        if snake.facing == 1 then
            snake.bodyY[1] = snake.bodyY[1] - 35
        elseif snake.facing == 2 then
            snake.bodyX[1] = snake.bodyX[1] - 35
        elseif snake.facing == 3 then
            snake.bodyY[1] = snake.bodyY[1] + 35
        elseif snake.facing == 4 then
            snake.bodyX[1] = snake.bodyX[1] + 35
        end
    end

    if snake.bodyX[1] == food.x then
        if snake.bodyY[1] == food.y then
            food.x = love.math.random(1, 19) * 35
            food.y = love.math.random(1, 19) * 35
            snake.length = snake.length + 1

            snake.bodyX[snake.length] = snake.bodyX[snake.length - 1]
            snake.bodyY[snake.length] = snake.bodyY[snake.length - 1]
        end
    end

    for i = 1, snake.length, 1 do
        snake.bodyX[i] = snake.bodyX[i - 1]
        snake.bodyY[i] = snake.bodyY[i - 1]
    end

    if update == snake.speed then
        update = 0
    else
        update = update + 1
    end
end

function love.draw()
    love.graphics.setBackgroundColor(0.5, 0.9, 0.6)

    love.graphics.setColor(1, 1, 1)
    for i = 700, 1, -35 do
        love.graphics.line(i, 0, i, 700)
        love.graphics.line(i + 1, 0, i + 1, 700)
        love.graphics.line(0, i, 700, i)
        love.graphics.line(0, i + 1, 700, i + 1)
    end

    love.graphics.setColor(0, 0, 0)
    love.graphics.rectangle("fill", snake.bodyX[1], snake.bodyY[1], 35, 35) --This is were the error is

    love.graphics.setColor(1, 0.5, 0.5)
    love.graphics.rectangle("fill", food.x, food.y, 35, 35)
end

ASKING FOR ANY HELP

Posted: **Thu Jun 08, 2023 3:46 am**

lua uses array indices starting at 1, and in love.load() you set snake.bodyX = {0} where the implied index is 1 not 0. so just guessing that your problem is here:

Code: Select all

    for i = 1, snake.length, 1 do
        snake.bodyX[i] = snake.bodyX[i - 1]
        snake.bodyY[i] = snake.bodyY[i - 1]
    end

when i = 1, i- 1 = 0. and there is no snake.bodyX[0] set anywhere i.e. it is nil and thus snake.bodyX[1] is overridden and set to nil. this is repeated in the for loop through snake.length.

Posted: **Thu Jun 08, 2023 8:41 am**

Just a note, if you want to use C structs in LUA via FFI, instead of LUA tables they start with 0.

LÖVE

number expected, got nil

number expected, got nil

Re: number expected, got nil

Re: number expected, got nil