Best way of singleton in Objective-C

It’s very useful during iOS development

static GeneralData __strong *generalDataObject = nil;

@synthesize currentUser;

+(GeneralData *) getInstance
{
    static dispatch_once_t pred;
    dispatch_once(&pred, ^{
        generalDataObject = [self new];
    });
    return generalDataObject;
}

Usage

1. Add Data

   #import "GeneralData.h";
   
   - (IBAction) passValueButton:(id)sender {
   {
       User *user = [User new];
       user.name = "Mary Jane";
       user.age = "21";
       [GeneralData sharedInstance].currentUser = user;
   }

2. Read Data

   #import "GeneralData.h";
   
   - (void)viewDidLoad
   {
       [super viewDidLoad];
       User *loggedInUser = [GeneralData sharedInstance].currentUser;
       NSLog(@"Name : %@", loggedInUser.name);
       NSLog(@"Age : %@", loggedInUser.age);
   
   }

Reference : StackOverflow