How do I get the memory address of a variable, rather than the variable?

Tom2012 · October 2012

Hello

On my scene I have local score = 0;

On a class I would like to change the score to say 1.

If I run say Score:updateScore(score) it passes the value of score rather than the memory address.

Basically I'm trying to update score without using a global.

Thanks!!

Tom

Mells · October 2012

I believe you should be more specific and show more of your code so forum members could help you.
What you are trying to achieve doesn't sounds complex and should work with a quick fixes.

Is that what you are trying to achieve?

-- main.lua
local score = 1
print (score) -- 1
 
local scoreObj = Score.new(score)
score = scoreObj:updateScore(3)
 
print (score) -- 4

-- Score.lua
 
Score = Core.class(Sprite)
 
function Score:init(initScore)
     self.score = initScore
end
 
function Score:updateScore(addToScore)
     self.score = self.score + addToScore
     return self.score
end

Tom2012 · October 2012

Hi

I have a class that spawns characters on screen. Here's some of it...

function Caveman:onEnterFrame(event)
 
	if(self:collidesWith(self.hector.headAnimation)) then
 
-- caveman hits hector
		if(not self.collided and not self.onGround) then
			self.collided = true;
			score = score + 1;
			self.scoreText:setText(tostring(score)) -- increase score
			self:setVisible(false)
			self.hector.headAnimation:setAnimation("HECTOR_HEAD_MUNCH_2")
			self.blood:start()
			self.hector.headAnimation:playAnimation()
			self.munching = true;
		end
	end

I just can't figure out how to get this class to update the score on the scene:

Thanks for the example but I need to update the scene from the spawn class, not the other way around - if that makes sense.

Thanks Mells

bowerandy · October 2012

@Tom2012. You can't do it the way you suggest in Lua. You can't pass objects by pointer or by reference (as far as I know). However, what you can do is pass in a table which you can alter the contents of. And, indeed, that table could be the scene containing the score.

CaveScene=Core.class()
 
function CaveScene:init()
    self.score=0
end
 
...
 
function Caveman:bumpScore(scene)
    scene.score=scene.score+1
   ....
end

best regards

Mells · October 2012

I noticed in another discussion (I think it was you) that you said "it's amazing how a few words can make an application work" (you mistook stage for self or the other way around).
What you are trying to do can be solved but I think you should study more about the value of "self" (like, what is "self" at self.scoreText:setText(tostring(score))) and solve it yourself, so you will be able to solve the same kind of scope issues that you'll have to face in the future.

Tom2012 · October 2012

@bowerandy

Thank you. That's exactly what I was looking for.

Can't believe it was so simple. :0)

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