Question

I want to access a NSString from AppDelegate.m that is located inside ViewController.m.

I have a Single View Application, and i want to save my NSString using applicationDidEnterBackground: inside AppDelegate.m.

The NSString is located inside ViewController.m, and is not declared in AppDelegate.m.

I tried to declare it in AppDelegate.h and then access it in the ViewController.m (And reversed).

ViewController.h:

@interface MyAppViewController : UIViewController {
    NSString *MyString;
}

AppDelegate.m:

- (void)applicationDidEnterBackground:(UIApplication *)application {
   NSUserDefaults * defaults = [NSUserDefaults standardUserDefaults];
   [defaults setObject:MyString forKey:@"SavedString"];
   [defaults synchronize];
}

Answer 1

You can register MyAppViewController to observer UIApplicationDidEnterBackgroundNotification like this:

[[NSNotificationCenter defaultCenter] addObserver:self
        selector:@selector(goToBackground:) 
        name:@"UIApplicationDidEnterBackgroundNotification"
        object:nil];

and in the method goToBackground you can save in NSUserDefaults the MyString.