Scope Issue?

[Lacotemale]

Hey all,

So I've been working on a crappy RPG game for a while and progress was going well until I realized my code was just turning into a dogs dinner to put it politely. Its an absolute mess in my main and menu lua files.

I wanted to start cleaning up the main.lua file, so I've moved some collision functions into a separate Collisions.lua class/file. It doesn't work any longer and i'm not sure why. I feel like I'm having scope issues now? =/

Any help on this issue and advice for breaking up my code into more manageable chunks would be appreciated!

To test launch love file marked with fail, left click new game, then press Up arrow on your keyboard. You should get a nil error message and the line number.

[pgimeno]

In the non-working one, you don't ever define collisionUp, collisionDown etc. anywhere, yet you're attempting to call these as if they were functions, which they aren't, and your code crashes for that reason. To fix it, inside your functions you need to set self.collisionUp instead of returning the result, since you don't use the returned value anyway. Then in order to check it, you would use Collisions.collisionUp etc. (note the dot and the lack of parentheses) instead of Collisions:collisionUp(...) etc. (note the colon and the parentheses).

There are other problems, though.

When calling checkUpCollision etc. with the last object checked, it will overwrite the previous setting of collisionUp etc. because if there's no collision with that last object, it will be set to false regardless of whether there was a collision with another object first. The consequence is that only the collision with that last object counts. To fix this, you set it to false once at the beginning only, and the function that checks collisions needs to set it to true when there's a collision, but not touch it when there isn't. Something like this:

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--- in classes/Collisions.lua ---
function Collisions:checkUpCollision(item, player)
    if Collisions:box_collision(player.x, player.y-5, player.w, player.h, item.x, item.y, item.w, item.h) and item.itemType == 100 then
        self.collisionUp = true
    end
end

--- in main.lua ---
if startGame == true then
    -- Clear all collision flags to check this round
    Collisions.collisionUp = false
    ...

    -- Check for collisions between the player and the items on the map
    for i = 1, #itemsOnMap do
        ...
            Collisions:checkUpCollision(itemsOnMap[i], player)
            ...

Another problem in the 'working' version is that 'and' has more priority than 'or', which causes this line:

Code: Select all

                if down('w') or down('up') and collisionUp== false then

to be interpreted as if it was written like this:

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                if down('w') or (down('up') and collisionUp== false) then

The consequence is that with w/a/s/d you skip collision tests (in your "working" version). To fix it, put parentheses around the first two conditions, like this (and also I've changed it to Collision.collisionUp as per above):

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                if (down('w') or down('up')) and Collision.collisionUp== false then

[Lacotemale]

Wow, thanks dude!

I think self was the missing piece of the puzzle. I kept trying "this.var" but I spend too long on Javascript these days and not enough time on other languages. Now time to restructure my whole codebase so I feel I can get back working on this.

[Lacotemale]

Why does return not work from external files?

Code: Select all

Responsive {}

function Responsive:getCoordsByPercent(percentW, percentH)
	self.width, self.height = love.graphics.getDimensions( )
	self.w = (self.width/100)*percentW
	self.h = (self.height/100)*percentH
	return self.w,self.h
end

Called by:

Code: Select all

plrX, plrY = Responsive:getCoordsByPercent(50,50)

Error:

attempt to call global Responsive a nil value

[s-ol]

You omitted an equals-sign (=) on the first time there, which makes it Responsive {} which is the same as Responsive({}).

[Lacotemale]

Oh dear that was embarrassing! Thanks!