Transition from One view controller to another - UI Update

Question

Lets say I have two viewcontrollers A and B. From A to B, I add the viewcontroller B on top of A. On popping, I call the following method in B

 -(void)viewWillDisappear:(BOOL)animated{
    [super viewWillDisappear:animated];
    NSUserDefaults *userSettings = [NSUserDefaults standardUserDefaults];
    [userSettings setObject:firstName.text forKey:@"FN"];
    [userSettings setObject:lastName.text forKey:@"LN"];
    [userSettings synchronize];
 }

This userInfoUpdate method updates the NSUserDefaults object for the application. On returning back to viewcontroller A, I call the following method in A:

- (void)viewWillAppear:(BOOL)animated
{
  [super viewWillAppear:animated];
  NSUserDefaults *userSettings = [NSUserDefaults standardUserDefaults];
  profileTextField.text = [NSString stringWithFormat:@"%@ %@",[userSettings objectForKey:@"FN"],[userSettings objectForKey:@"LN"]];
}

But this doesn't update textfiled string. Any idea what I'm doing wrong here? Is there a better alternative?

why dont you read the data from NSUserDefaults from A's viewWillAppear? — hackerinheels, Jul 10 '14 at 21:02
@hackerinheels I'm reading the NSUserDefaults from A's viewwillAppear. I have made the edit. It looks like A's viewwillAppear is called before B's ViewWillDisappear — Siddharthan Asokan, Jul 10 '14 at 21:19
when i was testing with break points, A's viewwillAppear is called before B's ViewWillDisappear — Siddharthan Asokan, Jul 10 '14 at 21:24
May I suggest not using NSUserDefaults to share data across view controllers? NSUSerDefaults helps to save data across runs of app and you should continue to save the data in UserDefaults but to avoid these race conditions, you should use delegates or just a common DataModel. — hackerinheels, Jul 10 '14 at 21:25
@hackerinheels that sounds good too. I'm thinking of updating the NSUserDefault in the TapGesture method that causes the transition. This updates the NSUserDefault before the transition starts — Siddharthan Asokan, Jul 10 '14 at 21:28

score 1 · Accepted Answer · answered Jul 10 '14 at 21:32

I would recommend creating a class that acts as your data model that can be shared across the 2 Controllers. That way you would not have to worry about the Viewcontroller delegate function order.

@interface DataModel: NSObject
{
    NSString *firstName;
    NSString *lastName;
}

A contains object for DataModel:

@interface AVC:UIViewController
    @property (nonatomic, strong) DataModel *myDataModel

When A creates B and pass myDataModel to be updated by B and save it in viewDidDissapear.

A will now have updated value when it comes back in view and also saved across app launches and upgrades

score 0 · Answer 2 · answered Jul 10 '14 at 21:19

0

You don't call [userSettings synchronize] to save them.

answered Jul 10 '14 at 21:19

antonio

375
4
13

What happens if you update your field in viewDidAppear instead? – antonio Jul 10 '14 at 21:25
Also don't forget to call [super viewWillAppear:animated] and [super viewWillDisappear:animated] in corr.methods. Otherwise your app will behave incorrectly. – antonio Jul 10 '14 at 21:27

Transition from One view controller to another - UI Update

2 Answers2