Question

I have a problem. There is class to store game progress:

struct GameData {
    PackData & packDataById(LEVEL_PACK packId);
    int gameVersion;
    AudioData audio;
    PackData sunrise;
    PackData monochrome;
    PackData nature;
};

//singleton
@interface GameDataObject : NSObject <NSCoding>
{
    GameData data_;
}
+(GameDataObject*) sharedObject;
-(id) initForFirstLaunch;
-(GameData*) data;
-(void) save;
@end

and implementation:

@implementation GameDataObject

static GameDataObject *_sharedDataObject = nil;

+ (GameDataObject*) sharedObject
{
    if (!_sharedDataObject) {
        NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
        NSData *encodedObject = [defaults objectForKey:Key];
        if (!encodedObject)  {
            _sharedDataObject = [[GameDataObject alloc] initForFirstLaunch];
        }
        else {
            _sharedDataObject = (GameDataObject*)[NSKeyedUnarchiver unarchiveObjectWithData: encodedObject];
        }
    }
    return _sharedDataObject;
}

-(GameData*) data
{
    return &data_;
}

-(id) initForFirstLaunch
{
    self = [super init];
    if (self) {
        data_.audio.reset();
        data_.sunrise.reset();
        data_.monochrome.reset();
        data_.nature.reset();
        data_.gameVersion = 1;
        data_.sunrise.levelData[0].state = LEVEL_OPENED;
    }
    return self;
}

-(void) save
{
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    [defaults setObject:[NSKeyedArchiver archivedDataWithRootObject:self] forKey:Key];
    [defaults synchronize];
}

-(void) encodeWithCoder:(NSCoder *)encoder
{
    [encoder encodeInt:data_.gameVersion forKey:@"game-version"];
    [encoder encodeBytes:(uint8_t*)&data_.audio length:sizeof(AudioData) forKey:@"audio-data"];
    [encoder encodeBytes:(uint8_t*)&data_.sunrise length:sizeof(PackData) forKey:@"sunrise-pack"];
    [encoder encodeBytes:(uint8_t*)&data_.monochrome length:sizeof(PackData) forKey:@"monochrome-pack"];
    [encoder encodeBytes:(uint8_t*)&data_.nature length:sizeof(PackData) forKey:@"nature-pack"];
}

-(id) initWithCoder:(NSCoder *)decoder
{
    self = [super init];
    if (self) {
        data_.gameVersion = [decoder decodeIntForKey:@"game-version"];
        NSUInteger length = 0;
        {
            const uint8_t *buffer = [decoder decodeBytesForKey:@"audio-data" returnedLength:&length];
            assert(length);
            memcpy(&data_.audio, buffer, length);
        }

        {
            const uint8_t *buffer = [decoder decodeBytesForKey:@"sunrise-pack" returnedLength:&length];
            assert(length);
            memcpy(&data_.sunrise, buffer, length);
        }

        {
            const uint8_t *buffer = [decoder decodeBytesForKey:@"monochrome-pack" returnedLength:&length];
            assert(length);
            memcpy(&data_.monochrome, buffer, length);
        }

        {
            const uint8_t *buffer = [decoder decodeBytesForKey:@"nature-pack" returnedLength:&length];
            assert(length);
            memcpy(&data_.nature, buffer, length);      
        }
    }
    return self;
}

@end

It loads and saves itself correctly when save is called directly after initialization and nothing more is done.

But when I try a simple thing. I write in appDidFinishLaunching

GameDataObject *obj = [GameDataObject sharedObject]; 

Then everything is done – just one simple menu is loaded, and I minimize the application so

-(void) applicationDidEnterBackground:(UIApplication*)application
{
    [[CCDirector sharedDirector] stopAnimation];
    [[GameDataObject sharedObject] save];
}

is executed. And in this method obj is totally corrupted (before saving), sometimes it’s even seen with debugger as another class object.

What am I doing wrong?

EDIT

Just launching the app and minimizing it causes the same problem.

Answer 1

As I already mentioned in the comment, you have a memory bug when unarchiving the data using NSKeyedUnarchiver.

The method +[NSKeyedUnarchiver unarchiveObjectWithData:] returns an autoreleased object (you can tell from the naming convention: it doesn’t contain either new, alloc or copy) so you’d have to take ownership of the object by sending it a retain message. Now the object won’t be released by the autorelease pool at the end of the runloop.