Question

I think I understand the logic behind a delegate. I got more the problem to use it. How many steps are involved? Do I have to use existing delegates? Or can I use my one ones?

In my example I got the AppDelegate that created many views (Objects / View Controllers) of the same type. Each view should somehow call a method on the AppDelegate to close itself. This would happen when a button within the view is touched. The method call would include the reference of the view (self).

So far I know from other languages responders, event listeners and so on. They are so simple to use.

Can anybody help me. I just found massive examples with a lot of code in the web. It can’t be that hard to just call a parent in Objective C.

Answer 1

I think you should use for this the NSNotificationCenter

in you AppDelegate.m

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
...
...
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(buttonPushed:) name:@"ButtonPushedNotification" object:nil];
}

- (void)applicationWillTerminate:(UIApplication *)application
{
...
...
[[NSNotificationCenter defaultCenter] removeObserver:self];
}

this is the selector it will be called when the notification happens (we are still in the AppDelegate.m)

- (void)buttonPushed:(NSNotification *)notification {
NSLog(@"the button pushed...");
}

and in the ViewController.m when the button pushed (inside the method), you should post a notification like this:

{
...
[[NSNotificationCenter defaultCenter] postNotificationName:@"ButtonPushedNotification" object:nil];
...
}