Problem with SECS and self. [FIXED]

[xXOdysseusXx]

Hello! I'm a relatively new programmer. I learned how to use lua A LONG time ago with a little game called Roblox . Having moved to making my own 2d games with Love2d, I have encountered my first major problem. I can't seem to get self.(field) to be recognized as a value of the class. Here is my code for the class.

Code: Select all

require("lib/SECS")

Circle = class:new()

function Circle:init(dt)
	self.xspeed = 0
	self.yspeed = 0
	self.x = love.graphics.getWidth()/2 - 25
	self.y = love.graphics.getHeight()/2
	self.radius = 25
end

function Circle:draw()
	love.graphics.setColor(255,0,0)
	love.graphics.circle("fill",self.xpos,self.ypos,self.radius,50)
end

function Circle:update(dt)
	if self.y >= (love.graphics.getHeight() - self.radius)  then
	self.y = love.graphics.getHeight() - self.radius + 1
	end
	Circle:processKeys()
	Circle:processSpeed(dt)
end

function Circle:processKeys()
self.yspeed = 0
self.xspeed = 0
	if love.keyboard.isDown( "w" ) == true then
		self.yspeed = -100
	end
	if love.keyboard.isDown( "s" ) == true then
		self.yspeed = 100
	end
	if love.keyboard.isDown( "a" ) == true then
		self.xspeed = -100
	end
	if love.keyboard.isDown( "d" ) == true then
		self.xspeed = 100
	end
end

function Circle:processSpeed(dt)
self.y = self.y + self.yspeed * dt
self.x = self.x + self.xspeed * dt
end

My error will usually be something like "attempt to perform arithmatic on field 'blah' (a nil value). Anybody know what's wrong? If you need to see the full code please request.

[tentus]

I think I see your problem, let me trim this down for you:

Code: Select all

function Circle:init(dt)
	self.x = love.graphics.getWidth()/2 - 25
	self.y = love.graphics.getHeight()/2
	self.radius = 25
end

function Circle:draw()
	love.graphics.circle("fill", self.xpos, self.ypos, self.radius, 50)
end

Do you see it now?

Generally speaking, the error screens in Love are actually really useful. If they say they have an error with a variable name, tracking down that variable will often reveal your bug. This is why consistent, descriptive variable names are so important.

[xXOdysseusXx]

Thanks for the help! That was a simple error. But I'm still getting a problem.

This time I'll be more specific. It says

Code: Select all

Circle.lua:44: attempt to perform arithmetic on field 'y' (a nil value)

This one doesn't seem as easy as a fix.

EDIT: Like 44 is

Code: Select all

self.y = self.y + self.yspeed * dt

[tentus]

Ah, that one's a little trickier. The problem is that

Code: Select all

Circle:processKeys()
Circle:processSpeed(dt)

should be

Code: Select all

self:processKeys()
self:processSpeed(dt)

Get kikito or bartbes to explain how the semicolon + self works, I've always been rubbish at explaining it.

Also, a cool trick that you might find useful:

Code: Select all

if love.keyboard.isDown( "w" ) then

is the same as

Code: Select all

if love.keyboard.isDown( "w" ) == true then

[TechnoCat]

Get kikito or bartbes to explain how the semicolon + self works, I've always been rubbish at explaining it.

A call v:name(args) is syntactic sugar for v.name(v,args), except that v is evaluated only once.

[xXOdysseusXx]

Awesome thanks for the help guys!