Singleton function not retaining value

Question

I'll preface this question by saying that I am a total noob when it comes to Objective-C. So please, be patient with my question. :)

So here is my issue. I am basically allowing the user to 'rub out' an image by using alpha blending and such, and then converting the created texture to a CCSprite. I am then able to store the CCSprite in a function within my singleton class. Like so:

erasedTextureSprite = [CCSprite spriteWithTexture:darknessLayer.sprite.texture];

[[MySingleton sharedMySingleton] setRevealTexture:erasedTextureSprite];

Here is the setRevealTexture & getRevealTexture function as well as the revealTexture variable initialisation in my MySingleton.h file:

@interface MySingleton : NSObject
{
    CCSprite *revealTexture;
}

...

-(void) setRevealTexture: (CCSprite *) texture;
-(CCSprite *) getRevealTexture;

And here are both functions in my MySingleton.m file:

-(void) setRevealTexture: (CCSprite *) texture
{
    NSLog(@"set reveal texture.");
    revealTexture = texture;
    NSLog(@"%f", [revealTexture boundingBox].size.width);
}

-(CCSprite *) getRevealTexture
{
    NSLog(@"got reveal texture.");
    NSLog(@"%f", revealTexture.contentSize.width);
    return revealTexture;
}

If I set the reveal texture, and then get it right away, it seems to return the sprite correctly. However, if I set the texture and then transition to another scene, it seems to lose it's value, and throws me an error when I try and call the getRevealTexture function.

Question: Why is my function not retaining it's value when I transition between scenes?

If any more clarification is needed please let me know!

Answer 1

Practically there is no point in using your own setter and getter if your not doing anything fancy. What you are doing is using an iVar which should have been a strong property.

you could achieve the same by doing:

@property (nonatomic, strong) CCSprite *revealTexture;

in your header file. You would then get the following 2 functions by default:

[[MySingleton sharedMySingleton] revealTexture];
[[MySingleton sharedMySingleton] setRevealTexture:texture];

My next point of failure that I would presume if this doesn't work is that your singleton function is not working properly and your actually getting a new instance each time. You can easily find this out by doing in the debugger:

po [MySingleton sharedMySingleton]

And seeing the instance that is returned each time.

example for a basic singleton code:

static MySingleton *__sharedMySingleton = nil;

+ (id)sharedMySingleton {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        __sharedMySingleton = [MySingleton new]; // or a specific alloc init function
    });

    return __sharedMySingleton;
}

Due to the request - here is a short image to explain how to enter debugger commands in xcode 5: