Passing data from the FirstViewController to the LastViewController

Question

I have four viewControllers in my current design and I am designing an app to sell a product.

FirstViewController gets the product image and when user

Answer 1

Please don't use a singleton, even if the majority of users here tells you so. It would violate the SOLID-Principles for several reasons.

Instead just pass the object from ViewController to ViewController.

If all ViewController expect the same model class, you can create a common base class that has the property for the model.

it could have this method

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([segue.destinationViewControler isKindOfClass:[ProductAwareBaseViewController class]])
    {
        ProductAwareBaseViewController *vc = (ProductAwareBaseViewController *)segue.destinationViewControler;
        vc.product = self.product;
    }
}

---

I created an example project: https://github.com/vikingosegundo/ProductWizard

Note, that all view controller derive from ProductAwareBaseViewController

@import UIKit;

@class Product;

@interface ProductAwareBaseViewController : UIViewController
@property (nonatomic, strong) Product *product;
@end

---

#import "ProductAwareBaseViewController.h"
#import "Product.h"

@interface ProductAwareBaseViewController ()

@end

@implementation ProductAwareBaseViewController

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([segue.destinationViewController isKindOfClass:[ProductAwareBaseViewController class]]) {
        ProductAwareBaseViewController *vc = (ProductAwareBaseViewController *)segue.destinationViewController;
        vc.product = self.product;
    }
}
@end

This ViewController knows how to pass the model data of class Product to other instances of ProductAwareBaseViewController and subclasses of it.

All other view controller don't deal with passing the data, just adding each portion of data (name, description, price) to the model and displaying it.

i.e:

#import "EditNameProductViewController.h"
#import "Product.h"

@interface EditNameProductViewController () 
@property (weak, nonatomic) IBOutlet UITextField *nameField;
@end

@implementation EditNameProductViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.product = [[Product alloc] init]; 
}

- (IBAction)continueTapped:(id)sender {
    self.product.productName = self.nameField.text; 
}

@end

---

#import "EditDescriptionProductViewController.h"
#import "Product.h"

@interface EditDescriptionProductViewController ()
@property (weak, nonatomic) IBOutlet UITextField *descriptionField;
@property (weak, nonatomic) IBOutlet UILabel *nameLabel;
@end

@implementation EditDescriptionProductViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.nameLabel.text = self.product.productName;
}

- (IBAction)continueTapped:(id)sender {
    self.product.productDescription = self.descriptionField.text;
}

@end