Easy way to remove CocosNode objects from the Layer after action

cocos2d for iPhone » Programming » cocos2d support (graphics engine)

Easy way to remove CocosNode objects from the Layer after action

(16 posts) (8 voices)

Started 2 years ago by Alexey Patosin
Latest reply from srikanth

Tags:

Alexey Patosin
Member

I have some sprites and labels on the Layer. Before removing them they must do some actions (fade out for example). But after that I need to remove them from the layer with using [self removeChild:child cleanup:YES]. For that I create classes AutoCleaningSprite and AutoCleaningLabel which inherit Sprite and Label class and have new method:

- (void) removeFromParent{
CocosNode *parent=self.parent;
[parent removeChild:self cleanup:YES];
}

So for removing this objects after animation I used next actions:
[someAutoCleaningSprite runAction:
[Sequence actions:[FadeOut actionWithDuration:0.5],
[CallFunc actionWithTarget:someAutoCleaningSprite selector:@selector(removeFromParent)],nil]];

Is it correct method? Or may be there is something more simple way for removing CocosNode objects from the parent Object?

And I have another question - is it need to invoke [sprite release]; after [self removeChild:sprite cleanup:YES];?

Thanks..

Posted 2 years ago #
Codemattic
Moderator

"Is it correct method?"

Clever solution! If it works - its correct

"And I have another question - is it need to invoke [sprite release]; after [self removeChild:sprite cleanup:YES];?"

No. Not unless sprite is a member variable, which I cant tell from your code, but it probably isnt.

Posted 2 years ago #
vinhsteven
Member

if you use method spriteWithFile for Sprite, no need to invoke [sprite release]
else need. :)

Posted 2 years ago #

djdrzzy
Member

I've got an action that does the same thing so it's easy to sequence and you don't need callbacks everywhere.

@interface RemoveFromParentAction : InstantAction <NSCopying> {

}

+(id)action;

@end

@implementation RemoveFromParentAction

+(id)action {
	return [[[self alloc] init] autorelease];
}

-(void) startWithTarget:(id)aTarget
{
	[super startWithTarget:aTarget];
	[[aTarget parent] removeChild:aTarget cleanup:YES];
}

@end

Posted 2 years ago #

Taylor Jasko
Member

One question on this, how would you set this up if your refering to an index in the sprite?

Like CCSprite *sprite[index] = [CCSprite spriteWithFile:@"file.png"]...

When I tried to set this up, it removed every single thing in the sprite. I only want to remove one of the objects in the sprite. :D

Thanks guys! :)

Posted 2 years ago #
Taylor Jasko
Member

From above, I was able to get it to "work", but it removed the whole sprite. How would I get it to remove an individual index? Hmm, this is a bit tricky. :)

Posted 2 years ago #
Codemattic
Moderator
@tjasko1, I think you need to give us more code and explanation as to what you are trying to do.
```
CCSprite *sprite[index] = [CCSprite spriteWithFile:@"file.png"]...
```
that code looks pretty wrong to me.

Consider using NS collection classes like NSArray and NSMutableArray instead.
Posted 2 years ago #
Taylor Jasko
Member

@Codemattic:
I appreciate you informing me that my code looks wrong, but how would I use NSArray/NSMutableArray to store a sprite? Sorry, but I am new to Obj. C a bit. :)

I appreciate your help!

Posted 2 years ago #
Codemattic
Moderator
@tjasko1 I dont think I really understand what you are trying to do. The line of c code you had looks like you tried to combine *defining* an array with *accessing* a member of an array. Also with a c array it is up to you to retain an object that goes in to the array, and release an object that you are taking out of the array - it doesnt look like you are doing that, although I only have that code snippet to go by.

"how would I use NSArray/NSMutableArray to store a sprite?"

Assuming I want to have around 10 sprites (although the collection can grow or shrink) collected somewhere, I would define a property (retain) for:
```
NSMutableArray * mySprites;
```
then in that object's -init:
```
self.mySprites = [NSMutableArray arrayWithCapacity:10];
```
for accessing and inserting and deleting, read:

http://developer.apple.com/mac/library/documentation/Cocoa/Reference/Foundation/Classes/NSMutableArray_Class/Reference/Reference.html

and its parent class:

http://developer.apple.com/mac/library/documentation/Cocoa/Reference/Foundation/Classes/NSArray_Class/NSArray.html#//apple_ref/occ/cl/NSArray

Again, when posting try and explain what you are trying to accomplish, not just the code that isnt working. The title of this thread is about removing nodes from a layer after an action - is that what you are trying to do? If not, start your own thread with a descriptive title. Clearly explain what your goal is, what code you are using now, what you expect the code to do, and what it actually does instead.
Posted 2 years ago #
Taylor Jasko
Member

@Codemattic:
Yes, I was trying to remove node objects from the layer after a given action. But the thing is, because I had my code wrong, it was removing everything in the given sprite when I only wanted to remove the given index. Then I realized I had the wrong code. :D

I will be storring a lot more things in the array then ten, but from my understanding, the NSMutableArray can grow that index easily.

Thanks for your help! I'll read that all over and see if I can get this to finally work. I really appreciate it.

By the way, I happen to be a web-dev also, and it looks like they need to turn on the "word-wrap: break-word;" CSS property. Those URLs shouldn't be hanging out of the DIV like that. ;)

Posted 2 years ago #
Codemattic
Moderator

sound like you are on the right track now tjasko1

"Those URLs shouldn't be hanging out of the DIV like that"

hrm, in latest Firefox it wraps nicely, but you are right, in Safari the links just keep going and going...

Posted 2 years ago #
Taylor Jasko
Member

Thanks, Codemattic.

Well, every browser does render webpages differently...cough...IE. Might shoot an email over to the forum admin for that one. :)

Posted 2 years ago #
thefuzz
Member

re:

(void) removeFromParent{
CocosNode *parent=self.parent;
[parent removeChild:self cleanup:YES];
}

This strategy will work and I've found it very useful on my projects but one thing anyone who tries it needs to be aware of is a really really really evil memory bug that gets caused unless your careful. First off, the solution:

CocosNode *parent=self.parent;
[self retain];
[parent removeChild:self cleanup:YES];
[self autorelease];

Huge hack I know, and there are cleaner ways to do this but what happens if you don't is total heisenbuggery. Background:

- The NSInvocation object associated with the CallFunc action wants to write a 'return value' to an address in the NSInvocation object ... even if your function doesn't return anything.
- When you call removeChild:self cleanup:YES your sprites ref count goes down by one
- If your sprites ref count just hit zero (as it probably will), instead of being released 'at some time in the future' its going to get deallocated NOW. Thank apple for that little bit of magic they do when removing objects from NSArrays
- That deallocation cascades to the Action and then the NSInvocation all before your function returns.

If you've got anything else going on (other threads for instance that may be allocating something ... I'm looking at you OpenFeint) the NSInvocation return is about to write on some memory that no longer belongs to it ... and you will likely not find out about it until way past too late ;)

Posted 2 years ago #
Codemattic
Moderator

@thefuzz, great tip!

Posted 2 years ago #
ToniK
Member

Looks like only CCCallFuncND is using NSInvocation (at least in v.0.99.0). But it seems it could be replaced with performSelector:withObject:withObject: -- the same as in CCCallFunc and CCCallFuncN. Or maybe there's a reason to use exactly NSInvocation?

Posted 2 years ago #
srikanth
Member

How to retain the removed child?

Posted 2 years ago #

RSS feed for this topic

Reply

You must log in to post.