MVVM pattern and Storyboard iOS

Question

Does somebody can explain me how to implement MVVM pattern, when project includes Storyboard?

In many examples I saw that I have to use .xib files. And init ViewControllers like this:

-(instancetype)initWithModelView:(ViewModel *)viewModel{

    self = [super init];

    if(self){

        _viewModel = viewModel;
    }

    return self;
}

But with Storyboard I cannot init viewControllers, storyboard does it for me. Should I use properties instead?

i.e.

UINavigationController *nav = (UINavigationController *)[self.viewControllers objectAtIndex:0];
HomeViewController *hvc = (HomeViewController *)[nav.viewControllers objectAtIndex:0];
hvc.viewModel = viewModel;

self is UITabBarController.

Answer 1

You can initialize a viewModel property in prepareForSegue:sender: method of your UIViewController

Here is a link to a great sample MVVM app C-41 by Ash Furrow

An example of a viewModel initialization in that app:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    if ([[segue identifier] isEqualToString:@"showDetail"]) {
        NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];

        ASHDetailViewController *viewController = segue.destinationViewController;
        viewController.viewModel = [self.viewModel detailViewModelForIndexPath:indexPath];
    } else if ([[segue identifier] isEqualToString:@"editRecipe"]) {
        ASHEditRecipeViewController *viewController = (ASHEditRecipeViewController *)[segue.destinationViewController topViewController];
        viewController.viewModel = [self.viewModel editViewModelForNewRecipe];
    }
}