HELP!! attempt to get length of global 'bullets' (a nil value)

[samato31]

I can't figure out this error. I am pretty new to love2d. My knowledge is very limited. I would appreciate any guidance.

Error

bullet.lua:21: attempt to get length of global 'bullets' (a nil value)


Traceback

[love "callbacks.lua"]:228: in function 'handler'
bullet.lua:21: in function 'draw'
[love "callbacks.lua"]:168: in function <[love "callbacks.lua"]:144>
[C]: in function 'xpcall'

[steVeRoll]

The most likely reason is that you're trying to use the `bullets` variable without defining it, or before you've defined it. It would be easier to tell if you showed your code.

[samato31]

Here is my code. I am using bullets as a table.




function love.load()
bullets = {}
bullet.sprite = love.newImage('sprites/bullet.png')
end

function update(dt)

end

function love.keypressed(key)
if key == 'space' then
table.insert(bullets, {
x = player.x,
y = player.y,
})
end
end

function love.draw()
love.graphics.print("text", 200, 200)
if #bullets > 0 then
for bulletIndex, bullets in ipairs(bullets) do
love.graphics.setColor(0, 1, 0)
love.graphics.circle('fill', bullet.x, bullet.y, 5)
end
end
end

[steVeRoll]

This code doesn't give the same error you mentioned, however you seem to be mixing up the variables `bullets` and `bullet`.

For example, here:

Code: Select all

function love.load()
bullets = {}
bullet.sprite = love.newImage('sprites/bullet.png')
end

You're assigning a table to `bullets`, but then try to assign to `bullet.sprite` even though `bullet` wasn't defined.

And in this loop:

Code: Select all

for bulletIndex, bullets in ipairs(bullets) do
love.graphics.setColor(0, 1, 0)
love.graphics.circle('fill', bullet.x, bullet.y, 5)
end

You're calling the second iteration variable `bullets`, and then try to use `bullet`.

[pgimeno]

(dupe, see below)

[pgimeno]

With the info given, it's all guesswork, but the error message is telling a certain story.

The error happens inside `bullet.lua`, not inside `main.lua`, and it happens inside `love.draw()`. Specifically in line 21, when trying to take the length of a global variable called `bullets`, it's not initialized. This may seem surprising given that it's defined in `love.load()` in the same file.

My guess is that you have several `love.load()` events in different files, but that won't work. Only the last executed definition will prevail, and given that `bullets` is not defined, it seems to me that the one that prevails is not the one inside `bullet.lua`, yet the `love.draw()` that prevails is. That's why the error happens in `love.draw()` inside `bullet.lua` and why `bullets` is not defined.

You need a bit more organization. Place all the events in `main.lua`, and call each file's initialization, update and draw functions from them. There are several ways to do this, but a common approach is to have each file define a table with functions specific to the object it's dealing with, and then have `main.lua` call them from the appropriate event.

For example, instead of having `love.load()` and `love.draw()` inside `bullet.lua` (which is incorrect for the reasons mentioned earlier), you have them inside `main.lua` only. The file `bullet.lua` would declare a table which could be called Bullet, with upper-case B, where all bullet-related functions would go, for example taking your code:

Code: Select all

Bullet = {}

function Bullet.load()
    bullets = {}
    Bullet.sprite = love.graphics.newImage('sprites/bullet.png')
end

function Bullet.update(dt)

end

function Bullet.keypressed(uselesskey, key)
    if key == 'space' then
        table.insert(bullets, {
            x = player.x,
            y = player.y,
        })
    end
end

function Bullet.draw()
    love.graphics.print("text", 200, 200)
    for bulletIndex, bullet in ipairs(bullets) do
        love.graphics.setColor(0, 1, 0)
        love.graphics.circle('fill', bullet.x, bullet.y, 5)
    end
end

I've also fixed a couple things. Note that I've put the sprite inside `Bullet`. I've also removed the `if #bullets > 0` check because the loop will be executed zero times just fine when it's empty.

Finally, you've given no information about the rest of files in your project, but here's how your `main.lua` could look like, in the part that refers to bullets:

Code: Select all

require('bullet')

function love.load()
    Bullet.load()
end

function love.keypressed(...)
    Bullet.keypressed(...)
end

function love.update(dt)
    Bullet.update(dt)
end

function love.draw()
    Bullet.draw()
end

In each event, you would add calls to every other type of object you have (Player, Enemy, ...) as needed.

[samato31]

Thank you!
I added the bullet. functions to the main.lua function, and that fixed the problem.