Change NavigationBar Text from Different ViewController - ios

Question

I have a similar question posted prior to this one, but I now have a more clear question and more information along with code. I currently have a ViewController (SignUpViewController) with a UITextField and a UIButton. I also have another ViewController (ProfileViewController) that has a UINavigationBar. I want to be able to type a Username in the TextField in the SignUpViewController, tap the UIButton, then have the naviBar text in the ProfileViewController become set to the text in the SignUpViewController's TextField. Problem is, I can't access the UITextField from the ProfileViewController. I currently have an NSString in my AppDelegate called "titleString" and am trying to use that as some sort of a solution. Here is my code below if my question has completely thrown you off, as this is sort of difficult to explain over stack overflow:
SignUpViewController:
- (IBAction)submitButton {
ProfileViewController *profileVC = [[ProfileViewController alloc] initWithNibName:nil bundle:nil];
[self presentViewController:profileVC animated:YES completion:nil];
AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
appDelegate.titleString = #"Profile";
appDelegate.titleString = usernameTextField.text;
}
- (void)viewDidLoad {
AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
[super viewDidLoad];
}
ProfileViewController:
- (void)viewDidLoad {
AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
self.title = appDelegate.titleString;
[super viewDidLoad];
}
it all works fine until I tap the submitButton in the SignUpViewController. What is going on here?

Answer 1

There's several things you could do here to pass data between view controllers.
1) set up a delegate method. The profileViewController would be the delegate of the signInViewController. When the sign in button is pressed, the signInViewController calls the delegate method which the profileViewController is listening for, which passes the title to the profileViewController.
In signInViewController.h:
#protocol SignInDelegate
#required
- (void)didSignInWithTitle:(NSString*)title;
#end
#interface SignInViewController : UIViewController
#property (nonatomic, assign) id<SignInDelegate> delegate;
Then your ProfileViewController would be set as the delegate when you allocate it:
signInViewController.delegate = profileViewController
This is your ProfileViewController.h:
#import "SignInViewController.h"
#interface ProfileViewController : UIViewController <SignInDelegate>
Lastly, make sure your ProfileViewController implements the - (void)didSignInWithTitle:(NSString*)title; method.
2) You could use NSNotificationCenter to post a custom notification with the title attached. This would be useful if you had several other viewControllers that would want to set the title like the profile.
#define UPDATE_NAVBAR_TITLE #"UPDATE_NAVBAR_TITLE"
When the signInViewController is done:
[[NSNotificationCenter defaultCenter] postNotificationName:UPDATE_NAVBER_TITLE object:nil];
Then, make sure you add the ProfileViewController as an observer:
[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(navbarUpdated) name:UPDATE_NAVBAR_TITLE object:nil];
For what you're asking I recommend the first one. Good Luck!