Stupid Sprite / Action question « cocos2d for iPhone

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Stupid Sprite / Action question

(29 posts) (8 voices)

Started 2 years ago by Osiris
Latest reply from georgejcook

Tags:

Osiris
Member

Remember, I'm still a gentle Noob... The game that I started as a test is coming along nicely I think.

It started out as at test so it really wasnt thought out or "themed" as some of the more professional games, just a standard shooter.

It works now with a single ship and single alien and I can even do a power up and get a second ship...

Now for my $0.10 stupid question....

How do I setup the same action for multiple alien/monsters?

if I have set up a series of actions for the monster sprite to under take, How do I setup multiple instances to use the same actions?

I tried to use the same series of action for 2 fireball-bullets, but the second bullet just sat there until I created a totally seperate series of actions for the second bullet. It seems there should be a way to reuse actions, but i'm not far enough along to have figured it out.

I'm also planning on creating an array of monster sprites because I really don't understand allocating and deallocating sprites instances on the fly. If any one wants to give me a clue before I hurt myself, I would be eternally grateful!

Thanks!

Posted 2 years ago #
cjl
Member

Have you tried retaining the action?

Posted 2 years ago #
Osiris
Member

I dont know where to even look that up. I have heard of retaining, but sometimes people are so noob, they don't even know where to look for instructions that fit the situation. The example are cool, but most of the time its difficult to take those examples and make them fit a different kind of game, when you dont understand the underlying structures.

I have been eating, sleeping and breathing cocos2d and ObjC for a month now and I feel I have come a long way, but there is so far still to go!

Posted 2 years ago #
Osiris
Member

I just tried making an array of monster sprites but keep getting told that a "variable sized object may not be initiated. " It will probably take me a couple of days to figure out why it wont let me make an array of sprites.

Posted 2 years ago #
PhilM
Member

I suggest you read some of the docs on the apple developer portal, there's lots of good info their to help you bridge that gap ; )

Posted 2 years ago #
Osiris
Member

@PhilM - I wouldnt have gotten this far without them. Any suggestions on which ones to help with sprite allocation?

Posted 2 years ago #
Osiris
Member

One of the problems I find with Apple vs Cocos (and cocos is much better) is that at least for me, the syntax for doing things in Cocos2d is so different than Apple.

all the apple behaviors and properties seem needlessly complicated and alien.

Posted 2 years ago #
PhilM
Member

Apologies then ; )

I'm still learning about memory management. Apple do have some specific chapters on it, can't remember which docs its in off the top of my head.

I just searched for 'iphone memory management' and this came up:
http://kosmaczewski.net/2009/01/28/10-iphone-memory-management-tips/

Just had a quick skim, seems quite informative.

Posted 2 years ago #
cjl
Member

@Osiris:

Sorry, I'm a newbie like you, but I thought you might have already learned about retain. I'm at work now, so I can write more later if you're still stuck, but I think doing it yourself with some helpful clues from the community is best.

If you create an action, it is autoreleased after your program exits the local function it is created in, unless you call 'retain' on it. So, if you created an action in your init function but wanted to use it in some other function, you would assign it to an instance variable and retain it.

Anyway, do you know about the 'children' property of Cocosnode? If you added your sprites to a layer, you don't need to create your own array of sprites. The layer's 'children' is an array of the sprites you added. You could iterate through the children array, applying the action to each sprite. I think that's how other people do it. If you have more than one type of sprite on the layer, you can filter by the sprites tag property.

Sorry if I'm way off base above, but this is how I think it might work for you. By the way, have you read through the sample code in the tests? It seems like you already know enough, and reading though that code could really help you take the next step.

-cjl

Posted 2 years ago #
Osiris
Member

@PhilM - Thanks. I'm looking. Very deep stuff for me so far. Im just trying to create a way to have a dynamically variable # of aliens attacking without resorting to old tactics from BASIC. :)

Posted 2 years ago #
Osiris
Member

@ cjl - no, you are right on target. Thats exactly what I want to do. I just havent learned much more about layers and children than what I have seen in the examples.

and I havent run across any sample code yet to iterate through a list of subnode children sprites... but im all eyes and fumble-fingers!

Posted 2 years ago #

Osiris
Member

I really dont want to do

Sprite *ship1 = (Sprite *)[self getChildByTag:1];
Sprite *ship2 = (Sprite *)[self getChildByTag:2];

and

for (int i=0; i<10;i++) {

		Sprite * monster = [Sprite spriteWithFile:@"alien.png"];
		monster.position = CGPointMake(240.0f, 160.0f);
		monster.scale = 0.1f;
		monster.visible = NO;
		[self addChild:monster z:6 tag:20+i];
	 }

I know there is a better way, I just don't know how.

Posted 2 years ago #

Greg
Member

I'm working off of an example and here they build their things like projectiles at initialization, set their position offscreen (off camera?), and then when you want to use them, bring them out by "spawning them" in a new position.

But ultimately, to build your enemies or projectiles, basically anything with multiples or generic repetitions, you're probably going to loop over the same "build a monster" code. The cocos2d-iphone tips page (or somewhere, I forget) says to build Nodes in the init phase for performance reasons.

From a design perspective, I sub-classed Node with a class called Monster and in that init method I set my Cocos and Chipmunk initial state properties.

Does any of that help? Lol! I'm new here too...

Posted 2 years ago #
PhilM
Member

That seems ok, as gheidorn says, you'll need to loop through them somewhere to set them up. Be it directly in a a method as you show, or create an addMonster method that you call repeatedly from the loop. I'm all ears if theres a better way : )

Posted 2 years ago #
Osiris
Member

Thanks guys for the tips.. One thing im definitely having problems with is "arrays of objects" or "arrays of sprites" I can't seem to set up the structure to initialize them and then later to iterate through them in another function.

Posted 2 years ago #
PhilM
Member

You could try something along the lines of (this maynot be 100% correct, but should point you in the right direction)...

in your header:
NSMutableArray *items;

in your init (I'm not sure if the retain's needed here, if so don't forget to release in your dealloc):
items = [[[NSMutableArray alloc] init] retain];

then in your add loop, something like:
[items addObject:sprite];
for each of your sprites.

Later you could loop over them the old style,
int monsterCount = [items count];
for (int i = 0; i < monsterCount; i++) {
Sprite *sprite = [items objectAtIndex:i];
// do something
}

or use an enumerator:
for (Sprite *sprite in items) {
// do something
}

or, if you've added the monsters to their own layer, you could loop through the layers children using similar methods to above, without keeping track of your own array.

Posted 2 years ago #
Osiris
Member

@PhilM - THANK YOU... that makes more sense to me than 100 other examples...

there are clauses there I understand from PHP and python programming that I had totally forgotten about after soaking myself in this stuff for a month....

Thanks.

Incidently, I have been calling Sprite by "getChildByTag:" in the other functions. Is there a different way of calling them that respects arrays better? or do you pass the entire array of sprites to the function?

Posted 2 years ago #
Andrew
Member

@PhilM: As far as I know, any time you use New, Alloc, Copy or Retain, you have to have a release later.

items = [[[NSMutableArray alloc] init] retain];
is retaining items twice (once with the alloc and once with the retain), so would need to be released twice as well.

Somebody correct me if I'm wrong - this memory management stuff in Objective C is tricky stuff!

Posted 2 years ago #
PhilM
Member

your probably right Andrew, I was quickly looking at some old code from a crude prototype for examples, so that probably is wrong (hence the note). retain is also the first thing I usually try adding if I get access errors, but it may have just been left in by mistake.

@Osiris: no probs, I'm coming from a php background mainly, & find it useful to see examples with more generic syntax (if its available). I don't usually use tags with coco2d. I generally keep track of my nodes manually, or add certain node types to their own layers/parent-node, so I can easily loop through them later. But thats just my personal preference.

Posted 2 years ago #
Osiris
Member

"...
generally keep track of my nodes manually, or add certain node types to their own layers/parent-node, so I can easily loop through them later.
...
"

That is lightyears beyond me. I barely understand tags. I would rather do it a different way if I could figure it out.

Posted 2 years ago #
Osiris
Member
ok, point of confusion....I'm furiously rewriting code...

I have the function:
```
-(void) addMonster: (ccTime) delta
{

	int i = 0;

	for(Sprite *monster in aliens) {

		if(monster.visible == NO) {

			[monster setTag:20+i];
			[monster setVisible:YES];
			[monster setScale:0.1];
			[self addChild:monster z:6];
...
}
```
that is looking to see if it needs to add another monster to the grid.. If the monster has been marked not VISIBLE then its good to go back into the fight.

im doing the "[self addChild:monster z:6];" here because its the only way I know to hang the sprite onto the layer.

later on, in my removeMonsterSprite: function, Im trying everything I can to remove that sprite so I can hang it on the layer again when the addMonster cycle comes around again..

ive tried "[mySprite dealloc];" "[mySprite release];" "mySprite=nil" nd now
```
[LayerGame removeChild:mySprite];
```
I started with [Super removeChild:mySprite]; but that gave a warning and then so did "[layerGame.."

I know the answer is in here somwhere?
Posted 2 years ago #
Osiris
Member

I got it!

although im still not sure.... about the removing a sprite from a layer. but instead, I added the children all up when I created the array (thanks PhilM) and just using visible/invisible instead of trying to release or remove.

I now have a spaceship shooting game with a dynamic # of fighters that combine in tandem with powerups and a dynamic # of attacking aliens WOOHOO!

thanks guys... Now I have to start unstringing all my commented code!

Posted 2 years ago #
PhilM
Member

congrats ; )

Did you try [self removeChild:mySprite];? As you added it to 'self' thats probably where you should remove it from (if the remove code is in the same class/layer as the add code). Sounds like you've got around it now anyway.

Posted 2 years ago #
Osiris
Member

the major question is "SHOULD" I be trying to remove the sprite and the re-adding it in an emitter function? Or should I pre-allocate them and just hide the sprites when not in use? Right now I'm hiding and that seems to work pretty well, but I am trying to learn best practices.

It seems that the most dynamic way of handling a system with a large number of unknown sprites (ala gauntlet) would be to create and remove sprites as needed?

Posted 2 years ago #
georgejcook
Member

Andrew, no that's not right.

alloc only allocates memory, it doesn't increment the retain count, this is how you get zombie objects.

It's easy (well was for me at first) to get confused by properties which are synthesized by the @synthesize keyword that are described in your h file with the retain keyword (ie @property(retain) Foo *bar;

In that case you can do:
self.propertyWhichUsesRetainKeyword = [[Foobar alloc] init];

In this case an extra retain will over retain as you said, the reason is that the retain keyword on the @property declaration automatically generates code which will retain the value.

If you didn't @synthesize an @property(retain) property, or you wrote your own setter, that doesn't automatically retain, you will have to add the retain.

In short: alloc only allocates, something somewhere has to retain.

Posted 2 years ago #
Steve Oldmeadow
Administrator

@georgejcook, I think you need to read this:

http://developer.apple.com/documentation/Cocoa/Conceptual/MemoryMgmt/Articles/mmPractical.html

Posted 2 years ago #
PhilM
Member

Thanks georgejcook. That makes a little more sense. When I have a bit more time (probably not until next month), I plan to really go over my memory management skills (or lack of), and try to finally get my head round the different situations retain and release should/shouldn't be used. I'll post a follow up here, probably with questions, think a wiki page on the subject would be useful to a lot of people!

Edit: oops, looks like Steves link, shows alloc 'Allocates memory for an object, and returns it with retain count of 1.'

Posted 2 years ago #
Codemattic
Moderator

"alloc only allocates memory, it doesn't increment the retain count"
"In short: alloc only allocates, something somewhere has to retain."

It returns a new object that starts off with a retain count of 1, you dont need to retain it. It is up to you to release (or autorelease) it when you are done.

Posted 2 years ago #
georgejcook
Member

oops, thanks chaps, looks like I got confused!

Posted 2 years ago #

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