From: Riccardo Cecolin <rikiji@...>
Date: 2010-03-14T01:37:55+09:00
Subject: Re: Newbie Help : Object

Jerome David Sallinger wrote:
> Hello,
>
> This question may be more to do with my understanding of OOP that the
> actual contructs of Ruby so please be patient with me.
>
> I am interested in visualizing data so am teaching myself to Programming
> using Ruby via computer graphics. I am steadily building up my knowledge
> and experience by writing by and executing rudimentary code around the
> new thngs I learn. Now I'm stuck so i'll make the question as simple as
> I can:
>
> I create a window of Ball objects based on a Ball class that I have
> written. Each Ball object is instantiated at a randon x,y location on
> the screen and has random speed.
>
> Each Ball object is able to reverse its driection (bounce) if it hits
> the edge of the window.
>
> If I have two balls and I want to detect whether they instersect with
> each other as they move around the screen this is simple enough; the
> ball class has an intersect() method which i can use to pass in a
> reference to the other ball object. But what if there are are random
> number of balls. How do I make it such that any Ball object would be
> aware of the location of any other Ball object without having to resort
> to nested for loops where I check the location of each Ball against
> every other Ball?
>
> Any ideas
>   
You could set an array of n "Ball"s, check one against each other
element of the array then pop it out and repeat with remaining elements.
So the amount of intersect() methods you will call will be
\sum_{k=1}^{n-1} k  instead of (n-1)*(n). Feel free to correct me if i'm
wrong.

Riccardo