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Beginner Questions

(10 posts) (5 voices)

Started 2 years ago by tutukun
Latest reply from psionic

Tags:

question atlas sprite scene node

tutukun
Member
Hi,
I was trying to understand AtlasSpriteTest example. And there is a functoin
```
Class nextAction()
{

	sceneIdx++;
	sceneIdx = sceneIdx % ( sizeof(transitions) / sizeof(transitions[0]) );
	NSString *r = transitions[sceneIdx];
	Class c = NSClassFromString(r);
	return c;
}
```
i believe all that do is get the next scene idx then return it as a class. Why you have to create class out of string here? why cant just return an integer?
```
-(void) nextCallback: (id) sender
{
	Scene *s = [Scene node];
	[s addChild: [nextAction() node]];
	[[Director sharedDirector] replaceScene: s];
}
```
this is the part i dont get.
so function node belong to scenenode, it creates and returns a scenenode. so how its being called by nextAction? which just return a general class?

THank for reading :)

[edited: using backticks for code]
Posted 2 years ago #
ob1
Member

> i believe all that do is get the next scene idx then return it as a class. Why you
> have to create class out of string here? why cant just return an integer?

Well, it could have returned idx as an integer but then

[s addChild: [nextAction() node]];

Would not work.

So basically what does the code do:

"nextAction" requests the "class" for the code of the next scene. It is a different class for each scene. The list of classes is in an array of strings, that's why NSClassFromString is needed to get the class.

Once we have the classe, it's easy to instanciate it with "node". Node is cocos lazy (and uneficient way since it uses the autorelease pool) to [[alloc] init] the class.

So:

[s addChild: [nextAction() node]];

for for the 9th index will translate too:

[s addChild: [AtlasNewTexture node]];

Hope it's clearer now. What makes things confusing for beginners is that Cocos2D suffers from the blob or god antipattern. Everything is a node.

http://en.wikipedia.org/wiki/God_object

Posted 2 years ago #
Codemattic
Moderator

"Cocos2D suffers from the blob or god antipattern. Everything is a node."

Very true. Almost every non-trivial game project Ive tried to do on my own has ended up with a massive base "entity" type object too. Especially ones Ive worked on in C++. Id be interested in learning how to avoid that if you have any links/pointers.

thanks, Codemattic

Posted 2 years ago #
Codemattic
Moderator

btw, tutukun, you need to put commas between your tags.

question atlas sprite scene node

is one big tag!

Posted 2 years ago #
tutukun
Member

@ob1 thank you for the excellent reply. i've got it now :D

Posted 2 years ago #
Steve Oldmeadow
Administrator

ob1 said
> Hope it's clearer now. What makes things confusing for beginners is that Cocos2D suffers from the blob or god antipattern.
> Everything is a node.

I'll have to disagree, cocos2d uses the Composite pattern for the elements that are drawn and these derive from CocosNode. However, there are lots of important classes that aren't nodes - Action, Director, Grid, Texture2D, TextureAtlas, Texture and TouchDispatcher for example.

Posted 2 years ago #
Steve Oldmeadow
Administrator

@ob1 - I'm curious if you've ever used the Mobile 3D Graphics API for Java ME (since you were quoting Sun in your other thread)? If so what do you think about the design of that?

Posted 2 years ago #
ob1
Member

@Steve - It's the first time ever I code a game or do anything with graphics. I was quoting Sun just because of the MVC gfx. I still believe that it is not without reason that Sun, IBM and Apple are pushing MVC.

I guess my main beef with everything being a node is the "Scene" class. In most examples and tutorial I have seen, a Scene is used for anything vaguely related to view, model or controller.

Even the examples posted in the first post of this thread are "nodes" or even worse Layers. Look at Cocoa for example, ViewControlles CONTAIN a view, they are not views. A node is principally concerned with graphic operations and therefore should only be for graphic objects.

And the director should manage "scene" objects more like viewcontrollers than views in my opinion.

And when I see in instruments that my game spends most of its time (apart from eaglview) in "visitnodes", I believe that reducing what classes are nodes would not hurt.

So for Codemattic, as I mentioned in another thread, for me having well defined Model, views and controllers greatly help, as well as composite elements could (I haven't tried it yet):

http://www.cocos2d-iphone.org/forum/topic/195

I also personally use the factory pattern so that I can have various classes for entities or levels without having to shoehorn everything in one class.

Posted 2 years ago #
Steve Oldmeadow
Administrator

@ob1 - I don't see how the current design stops you from doing what you want, and it seems you have done it to a large extent. One of the things I love about cocos2d is that it is flexible in what architectures it supports and I wouldn't like to see it force people to go down a particular path. For example, some people we get coming to the forum have hardly even programmed at all but they still seem to be able to make a simple game by cobbling together some sprites with actions.

Posted 2 years ago #
psionic
Member

But while viewcontrollers contain views, views also contain subviews.
ie table view controllers table views, which contain cells which are
views as well. most of the actual functionality is in the table views,
not the table view controllers. and the functionality in the view
controller also has to do with the graphical layout of the table view.

Chris.

On Mon, Jun 22, 2009 at 5:15 AM, <cocos2d-iphone-discuss@gamesforfood.cl> wrote:
> ob1 says:
>
> @Steve - It's the first time ever I code a game or do anything with
> graphics. I was quoting Sun just because of the MVC gfx. I still believe
> that it is not without reason that Sun, IBM and Apple are pushing MVC.
>
> I guess my main beef with everything being a node is the "Scene" class. In
> most examples and tutorial I have seen, a Scene is used for anything vaguely
> related to view, model or controller.
>
> Even the examples posted in the first post of this thread are "nodes" or
> even worse Layers. Look at Cocoa for example, ViewControlles CONTAIN a view,
> they are not views. A node is principally concerned with graphic operations
> and therefore should only be for graphic objects.
>
> And the director should manage "scene" objects more like viewcontrollers
> than views in my opinion.
>
> And when I see in instruments that my game spends most of its time (apart
> from eaglview) in "visitnodes", I believe that reducing what classes are
> nodes would not hurt.
>
> So for Codemattic, as I mentioned in another thread, for me having well
> defined Model, views and controllers greatly help, as well as composite
> elements could (I haven't tried it yet):
>
> http://www.cocos2d-iphone.org/forum/topic/195
>
> I also personally use the factory pattern so that I can have various classes
> for entities or levels without having to shoehorn everything in one class.
>
> Read the whole thread.

Posted 2 years ago #

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