Something is wrong with singleton...unable adding a child because it is nil - objective-c

Question

I use a singleton the first time and I don't really know how to implement it...
Ok I need to explain some things:
In Hexagon.h (which inherits from CCNode) I want to create multiple sprites (here referred to as "hexagons"). However, they are not added to the scene yet. They are being added in the HelloWorldLayer.m class by calling Hexagon *nHex = [[Hexagon alloc]init]; . Is that correct ? Is it then iterating through the for loop and creating all hexagons or only one ?
Well anyways, I have a singleton class which has to handle all the public game state information but retrieving is not possible yet.For instance I cannot retrieve the value of existingHexagons, because it returns (null) objects. Either I set the objects wrongly or I am falsely retrieving data from the singleton. Actually, I would even appreciate an answer for one of these questions. Please help me. If something is not clear, please add a comment and I'll try to clarify it.
What I have right now is the following:
GameStateSingleton.h
#import <Foundation/Foundation.h>
#interface GameStateSingleton : NSObject{
NSMutableDictionary *existingHexagons;
}
+(GameStateSingleton*)sharedMySingleton;
-(NSMutableDictionary*)getExistingHexagons;
#property (nonatomic,retain) NSMutableDictionary *existingHexagons;
#end
GameStateSingleton.m
#import "GameStateSingleton.h"
#implementation GameStateSingleton
#synthesize existingHexagons;
static GameStateSingleton* _sharedMySingleton = nil;
+(GameStateSingleton*)sharedMySingleton
{
#synchronized([GameStateSingleton class])
{
if (!_sharedMySingleton)
[[self alloc] init];
return _sharedMySingleton;
}
return nil;
}
+(id)alloc
{
#synchronized([GameStateSingleton class])
{
NSAssert(_sharedMySingleton == nil, #"Attempted to allocate a second instance of a singleton.");
_sharedMySingleton = [super alloc];
return _sharedMySingleton;
}
return nil;
}
-(id)init {
self = [super init];
if (self != nil) {
}
return self;
}
#end
Hexagon.m
-(CCSprite *)init{
if( (self=[super init])) {
NSString *mainPath = [[NSBundle mainBundle] bundlePath];
NSString *levelConfigPlistLocation = [mainPath stringByAppendingPathComponent:#"levelconfig.plist"];
NSDictionary *levelConfig = [[NSDictionary alloc] initWithContentsOfFile:levelConfigPlistLocation];
NSString *currentLevelAsString = [NSString stringWithFormat:#"level%d", 1];
NSArray *hexPositions;
if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad){
hexPositions = [[levelConfig valueForKey:currentLevelAsString] valueForKey:#"hexpositionIpad"];
}
else{
hexPositions = [[levelConfig valueForKey:currentLevelAsString] valueForKey:#"hexpositionIphone"];
}
NSString *whichType = [NSString stringWithFormat:#"glass"];
CGSize screenSize = [CCDirector sharedDirector].winSize;
if ([whichType isEqualToString:#"stone"]){
hexagon = [CCSprite spriteWithFile:#"octagonstone.png"];
}else if([whichType isEqualToString: #"glass"]){
hexagon = [CCSprite spriteWithFile:#"octagoncolored1.png"];
}else if([whichType isEqualToString: #"metal"]){
hexagon = [CCSprite spriteWithFile:#"octagonmetal.png"];
}
NSMutableDictionary *eHexagons =[[GameStateSingleton sharedMySingleton] getExistingHexagons];
for (int i=0;i < [hexPositions count];i++){
CGPoint location = CGPointFromString([hexPositions objectAtIndex:i]);
CGPoint nLocation= ccp(screenSize.width/2 + 68 * location.x,screenSize.height/2 + 39 * location.y);
NSString *aKey = [NSString stringWithFormat:#"hexagon%d",i];
hexagon =[CCSprite spriteWithFile:#"octagoncolored1.png"];
hexagon.position = nLocation;
[eHexagons setObject:hexagon forKey:aKey];
[self addChild:[eHexagons valueForKey:aKey] z:3];
[[GameStateSingleton sharedMySingleton]setExistingHexagons:eHexagons];
}
NSLog(#"these are the existinghexagons %#", existingHexagons);
//This returns a dictionary with one (null) object
}
return hexagon;
}
HelloWorldLayer.m -> -(id)init method
Hexagon *nHex = [[Hexagon alloc]init];

Answer 1

First of all, it returns null because the existingHexagons array has never been initialized in the first place. Go to the init function of your singleton and add:
existingHexagons = [[NSMutableArray alloc]init];
As for your For Loop question, I did not get it. I recommend making one StackOverflow question per query instead of putting two in one.