MVVM router example

HPQuizRouter.h

@interface HPQuizRouter

- (void)navigateToSelectedQuiz:(id<HPQuizState>)quizState from:(UIViewController*)screen;

- (void)prepareForSegue:(UIStoryboardSegue*)segue sender:(id)sender;

@end

HPQuizRouter.mm

@implementation HPQuizRouter

- (void)navigateToSelectedQuiz:(id<HPQuizState>)quizState from:(UIViewController*)screen
{
    // wraps segue ids. They should not appear in the client code
    
    if ([quizState isCompleted])
    {
        [screen performSegueWithIdentifier:kSegueToAlreadyCompletedQuizScreen sender:screen];
    }
    else
    {
        [screen performSegueWithIdentifier:kSegueToSelectedQuiz sender:screen];
    }
}


- (void)prepareForSegue:(UIStoryboardSegue*)segue sender:(id)sender
{
  if ([segue.identifier isEqualToString:kSegueToSelectedQuiz])
  {
    MySelectedQuizVC* nextVC = objc_member_of_cast<MySelectedQuizVC>(segue.destinationController);
    nextVC.viewModel = [MyFactory buildVmForXYZ];
    nextVC.router = [MySelectedQuizVCRouter new];
  }
}

@end
 

QuizQuestionVC.h

@interface QuizQuestionVC : UIViewController

// to be injected
@property (nonatomic, strong) HPQuizRouter* quizRouter;
@property (nonatomic, strong) id<HPQuizListVM> quizVM;

@end

QuizQuestionVC.m

- (void)tableView:(UITableView*)tableView
    didSelectRowAtIndexPath:(NSIndexPath*)indexPath
{
        // user's action
    [self.router navigateToSelectedQuiz:self];
}


-(void)viewModelDidLoadSomethingAndShouldNavigate:(id)myViewModel
{
    // data flow driven
    [self.router navigateToSelectedQuiz:self];
}

- (void)prepareForSegue:(UIStoryboardSegue*)segue sender:(id)sender
{
    // navigation logic and dependency injection delegated to a separate class
    [self.router prepareForSegue:segue sender:self];
}


- (void)viewDidLoad
{
    [super viewDidLoad];

    // lights out if injection has not been done properly
    NSParameterAssert(nil != self.quizRouter);
    NSParameterAssert(nil != self.quizVM);
}