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

    firstViewController.m
    #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

    secondViewController.m
    #import "GeneralData.h";

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

Reference : StackOverflow