refresh data after entering a foreground

Question

After changing the default settings, I would like to refresh data of myViewController when I enter the foreground in AppDelegate. What I do is

AppDelegate.m

Answer 1

You have many problems with your code.

confusion between Foreground and Background

- (void)applicationWillEnterForeground:(UIApplication *)application {
    NSLog(@"APPLICATION WILL ENTER BACKGROUND");
    ...

Well, no, it will enter FOREGROUND, and is leaving BACKGROUND.

missing super call in viewDidLoad

- (void)viewDidLoad {
    ...

You shall add a [super viewDidLoad];

direct call to viewDidLoad

- (void)applicationWillEnterForeground:(UIApplication *)application {
    [myViewController viewDidLoad];
    ...

Well, no, do not call viewDidLoad yourself, as it is supposed to only be called once by the system. Super classes or sub classes may be incompatible with multiple calls.

unbalanced observers

- (void)viewDidLoad {
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(updateSettings:) name:UIApplicationDidFinishLaunchingNotification object:nil];
    ...

By calling viewDidLoad multiple times, you were actually registering multiple observers for the same event. You need to have in your code a symmetry with as many calls to removeObserver than addObserver (note that you can also remove multiple observers at the same time).

missing implementation?

[[NSNotificationCenter defaultCenter] addObserver:self
                                   selector:@selector(defaultsChanged:)
                                       name:NSUserDefaultsDidChangeNotification
                                     object:nil];

Well, we don't see your implementation of defaultsChanged:, so it's unclear what you were trying to achieve. Was it to set a BOOL to YES and subsequently check that value to determine if preferences were changed? Something like that?

- (void)defaultsChanged:(id)notif {
    self.refreshData = YES;
}

- (void)applicationWillEnterForeground:(UIApplication *)application {
    if (self.refreshData) {
        self.refreshData = NO;
        // we refresh data now
        ...
    }
}