[XMark]

I was just wondering, say you have two different instances of an object, and you want one instance to get data from another instance (for example, a bunch of enemies doing collision detection on each other)

I can think of several ways to do this, though what I'd really like to know is the strict OOP Nazi approach to it.
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Mark Hall
Abstract Productions
I PLAYS THE MUSIC THAT MAKES THE PEOPLES FALL DOWN!

[Mandrake]

easiest way->
make x/y public

somewhat strict OO way->
x/y private, make a function that is a friend function that can access the variables.

overly complicated way for strict OOP:
Create a struct that is made for x/y information, and maybe h/w information (for collision). Have a function that returns this struct from private data. That way, other objects can have access to the data without directly getting the data (a basic GET function).

This being, the whole point of public/private data is how much access you want to give to external etinties, and it's only worthwhile when creating a library.

Think of it this way- Why does public and private settings exist OOP terminology? So that when someone else uses your class, they don't write the wrong information into variables. It's protecting the data from getting corrupted. At least, as far as I know, is the intent. So making some data public really isn't un-OO. Just know the risks. Simple is better, IMHO, so just make it public.
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"Well, last time I flicked on a lighter, I'm pretty sure I didn't create a black hole."-
Xmark

http://pauljessup.com

[DrunkenCoder]

[tcaudilllg]

The JS way:

foo.bar = eval(bar.foo.toSource());

[janus]

[XMark]

[RuneLancer]

[XMark]

ah yes, I actually do something similar to that in the ARC engine. When an NPC moves, it places a temporary collision tile in the space it's going to move into, then gobbles it up when it arrives, though the rest of the collision detection between NPC's is done by the NPC object calling a collision-checking function outside of the NPC's object. It works good, but it just feels like a cheap hack to me.

Anyway, the reason I'm asking is that I'm beginning to work on a turn-based strategy game, but at the same time I'm using this as an excercise to improve my coding style (prompted by my dismal performance at that job interview).
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Mark Hall
Abstract Productions
I PLAYS THE MUSIC THAT MAKES THE PEOPLES FALL DOWN!

[js71]

[RuneLancer]

[biggerUniverse]

NOTE: only works for tile-based engines.

Well, you should probably use something in between. When an NPC moves onto a tile, it should register with that tile. Say: tile.setOccupier(object);

(Don't gobble this on arrival)

Then when another NPC comes along, it just asks the tile it's trying to move to: tile.getOccupier();. Null here would be significant- it means there is no occupier, and the tile is free. When an NPC moves OFF a tile, it simply calls tile.setOccupier(null); on its old home.

This way, you're not checking every NPC every time you want to move. For tile engines, this is very optimal.

For free-moving NPCs/Objects, use recursive quadrants (Quadtrees) to handle the lookups quickly.
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We are on the outer reaches of someone else's universe.

[RuneLancer]

Personally, I'd give every area on the map a single byte to determine occupation, and have each bit represent one "height" unit. Then I'd just work with bits.

Suppose you have a bridge, technically two people should be able to occupy the same space. The previously mentionned methods would not allow this, and walking across the bridge when someone's underneath it would lead to walking on occupied tiles. But with this method, suppose the bridge goes up 3 units above the ground and you're walking underneath an NPC on this bridge, the tile occupation would be "8" (00001000) Bit 1 (ground level) isn't set, so you can freely pass underneath the NPC.

This isn't even an issue if you compare with ranges, but that means comparing against every occupied region (hardly a problem on a modern PC; even with 50 objects testing against each other every frame, that's only 2,450 comparaisons.)
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Endless Saga
An OpenGL RPG in the making. Now with new hosting!

[tcaudilllg]

[biggerUniverse]

Galby, although JS is generally a useful programming language, I think that in this thread it's doing little more than getting in the way of helping XMark. I'm going to assume that XMark is not interested in how the problem would be solved in JS, since I don't think his code is written in JS.

I believe that it is unnecessary to continue talking about JS (Janus, you too) in this thread. If you find that you can take the knowledge you have of JS and apply it to C++, please feel free to post that application of your knowledge (test it first).

EDIT: The downside of your method, RuneLancer, is that you don't know who is occupying a tile. Further, I'd use layers of tiles if you are going to have bridges etc.
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We are on the outer reaches of someone else's universe.

[RuneLancer]