How to open an existing viewcontroller in ios

Question

I need to open existing viewcontroller from AppDelegate while receiving push notification. Currently i am opening new one every time so issue is that it is called viewDidLoad every time and all variable are reinitialized again and again.

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
{

[[NSUserDefaults standardUserDefaults] setObject:@"Yes" forKey:@"Got Message"];
            [[NSUserDefaults standardUserDefaults] setObject:userInfo forKey:@"message"];
            [[NSUserDefaults standardUserDefaults]synchronize];            

            HomeViewController* room = [[HomeViewController alloc] init];
            [self.window.rootViewController presentViewController:room
                                                         animated:NO
                                                       completion:nil];



}

Answer 1

Try to do so:

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
    {

    [[NSUserDefaults standardUserDefaults] setObject:@"Yes" forKey:@"Got Message"];
                [[NSUserDefaults standardUserDefaults] setObject:userInfo forKey:@"message"];
                [[NSUserDefaults standardUserDefaults]synchronize];            

                [self.window.rootViewController presentViewController:self.room
                                                             animated:NO
                                                           completion:nil];



    }

    - (UIViewController *)room {
    if (_room == NULL) {
    _room = [[HomeViewController alloc] init];
    }
    return _room;
    }

Then you can reuse your view controller (However, it will exposure the view controller in your AppDelegate, which may be a taste in clean code).

Answer 2

Since you want to use a existing view controller, why do you use the code HomeViewController* room = [[HomeViewController alloc] init]; ?

Follow your goal, my suggestion is use a property to retain the existing view controller, just like:

@property (strong, nonatomic) UIViewController *existingViewController;

and you

[self.window.rootViewController presentViewController:existingViewController
                                                     animated:NO
                                                   completion:nil];

Answer 3

You can get UINavigationController in AppDelegate meethod

UIViewController *yourViewController = //your view controller to show after push
UINavigationController *navController = self.window.rootViewController;
[navController popToViewController:yourViewController animated:YES]