Cocos2D Z values between a sprite and a label - cocos2d-iphone

Question

Firstly thanks for taking the time to look at this question.
The problem I am having is with Cocos2d and the Z values which determine where the sprites are in relation to other objects.
I have a sprite ('Ball') and also a score label ('scoreLabel') using CCLabelBMFont and I want the 'Ball' sprite to appear in front of the score label. I am currently attempting this via the z values but it is not working.
I am not sure if its because one is a sprite and the other is not as the below will work when the other object is a sprite but if anyone can point me in the direction of where I am going wrong it would be greatly appreciated.
Relevant code is listed below.
// Constants.h
// TestGame
//#ifndef SpaceViking_Constants_h
//#define SpaceViking_Constants_h
#define kBallSpriteZValue 10
#define kBallSpriteTagValue 0
#define kNewScoreTagValue 0
#define kNewScoreZValue 25
// GamePlayLayer.m
// TestGame
#import "Constants.h"
-(id)init {
self = [super init];
if (self !=nil) {
Ball *ball = [[Ball alloc]
initWithSpriteFrame:[[CCSpriteFrameCache
sharedSpriteFrameCache]
spriteFrameByName:#"Ball_1.png"]];
[ball setPosition:ccp(screenSize.width * 0.19f,
screenSize.height * 0.19f)];
[sceneSpriteBatchNode
addChild:ball
z:kBallSpriteZValue
tag:kBallSpriteTagValue];
scoreLabel = [CCLabelBMFont labelWithString:#"0"
fntFile:#"Test.fnt"];
scoreLabel.position = ccp(screenSize.width * 0.5f, screenSize.height * 0.9f);
[self addChild:scoreLabel
z:kNewScoreZValue tag:kNewScoreTagValue];
}
return self;
}

Answer 1

Things you need to know
z ordering only matters if you nodes are siblings (they have the same parent); the z order is not global in Cocos2d
If no z order is defined than the order of adding the children is used to determine in which order they are rendered
What this means for your use case
Setting the z order for your to CCNode objects as is will make no difference, because they are not siblings.
The ball is the the child of sceneSpriteBatchNode but the label is the child of self.
This means that the ball will already show behind the text, assuming this is your hierarchy:
->sceneSpriteBatchNode->ball
->label
Bonus stuff
Instead of using defines in your code, consider using an enum like so
typedef NS_ENUM(NSUInteger, UTzOrder) {
ballsZorder = 0,
labelsZorder = 1,
otherStuffZorder = 2
};
This is better because the compiler knows that you are using the right types, it is prettier and easier to change.
Remember this is only when they are siblings.

Answer 2

looking at your code I see that you have given higher z value to your label. Instead of giving higher value to your sprite, you should give it to your sprite(ball) so it will be placed on the label.
Whenever you create any objects in cocos2d it will be placed at default z=0 , you can set z value to put object behind current object or above current object. you can set negative z value also to put your label behind your sprite.
ex:
define kBallSpriteZValue 0 //this value should be greater in your case
define kNewScoreZValue -1
you can also reorder your z values later
[self reorderChild:spritename z:newzvalue];