Question

what method within a ViewController’s class can I call to check when it has been brought to the foreground?

For example Im looking at a page on my application and I decide to close the application and go back to it later. When I go back to it the same view as I was looking at was on the screen. However… As soon as I open the application I want to segue over to another view.

How can I do this?

Currently trying this:

 - (void) applicationDidBecomeActive:(NSNotification*) notification
{
    [self checkActivity];
    // Do your stuff here
}


- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
        [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(applicationWillEnterForeground:)
                                                     name:UIApplicationWillEnterForegroundNotification
                                                   object:nil];
        [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(applicationDidBecomeActive:)
                                                     name:UIApplicationDidBecomeActiveNotification
                                                   object:nil];
    }
    return self;
}

- (void)checkActivity{
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    NSLog(@"Checking if re-authentication required...");
    if([[defaults objectForKey:@"shouldgotologin"] isEqualToString:@"yes"]){
        NSLog(@"View Should go to login...performing segue");
        [defaults setObject:@"no" forKey:@"shouldgotologin"];
        [defaults synchronize];
        [self performSegueWithIdentifier:@"backtologin" sender:self];
    } else {
        NSLog(@"Should go to login is not true.");
    }
}

Answer 1

Register your view controller to observe UIApplicationWillEnterForegroundNotification:

1) Inside view controller’s init method:

[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(applicationWillEnterForeground:)
                                             name:UIApplicationWillEnterForegroundNotification
                                           object:nil];

2) Inside view controller’s dealloc method:

[[NSNotificationCenter defaultCenter] removeObserver:self];

3) Also, have your view controller implement this method:

- (void) applicationWillEnterForeground:(NSNotification*) notification
{
    // This method will be called just before entering the foreground;
    // Do your stuff here
}

If the timing of UIApplicationWillEnterForegroundNotification doesn’t suit you, check all the available notifications for UIApplication here:
http://developer.apple.com/library/ios/#DOCUMENTATION/UIKit/Reference/UIApplication_Class/Reference/Reference.html