iOS UIViewAnimation not working

Question

I have a master detail application that when the detail view appears and a string is empty, I want it to present a new view through a UIViewAnimationFlip. The animation is working, but it keeps flipping to itself, not the view controller I initiated. Any help would be great!

- (void)viewDidAppear:(BOOL)animated {

    if (masterView.parserURL == nil) {

        LoginViewController *login = [[LoginViewController alloc] init];

        [UIView beginAnimations:nil context:NULL];
        [UIView setAnimationDuration:0.8];
        [UIView setAnimationTransition:UIModalTransitionStyleFlipHorizontal
                               forView:self.view
                                 cache:YES];

        [self.navigationController presentViewController:login 
                                                animated:YES 
                                              completion:nil];

        [UIView commitAnimations];
    }
}

Answer 1

I agree that you should be doing this modally, instead of just adding a subview. In your example code you are animating twice, because the presentviewcontroller method is animating itself already. Try removing the other animation code as follows:

LoginViewController *login = [[LoginViewController alloc] init];
login.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;

[self presentViewController:login 
                   animated:YES 
                 completion:nil];

Answer 2

I'm suggesting simply:

- (void)viewDidAppear:(BOOL)animated {

    if (masterView.parserURL == nil) {

        LoginViewController *login = [[LoginViewController alloc] init];

        login.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;

        [self presentViewController:login
                           animated:YES
                         completion:nil];
    }
}

Note, there's an interesting question of how the login screen is supposed to update that parserURL field in masterView. You might add a property to your login controller that is a pointer to masterView, so that it has a mechanism to update the parserURL. Thus it might be like:

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    if (masterView.parserURL == nil)
    {
        LoginViewController *login = [[LoginViewController alloc] init];

        login.masterView = masterView;

        login.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;

        [self presentViewController:login
                           animated:YES
                         completion:nil];
    }
}

Then your login controller can now update the parserURL via:

self.masterView.parserURL = ... // set it as appropriate