Basic singleton

MyObject.h

@interface MyObject : NSObject

@property (nonatomic, strong) NSMutableArray *myArray;

+ (MyObject *)sharedInstance;

@end

MyObject.m

@implementation MyObject

+ (MyObject *)sharedInstance
{
    static dispatch_once_t dispatchOncePredicate = 0;
    __strong static MyObject *_sharedObject = nil;
    dispatch_once(&dispatchOncePredicate, ^{
        _sharedObject = [[MyObject alloc] init];
    });
    return _sharedObject;
}

- (id)init
{
    self = [super init];
    if (self) {
        [self setMyArray:[NSMutableArray array]];
    }
    return self;
}

@end