iOS - Calling App Delegate method from ViewController
You can access the delegate like this:
MainClass *appDelegate = (MainClass *)[[UIApplication sharedApplication] delegate];
Replace MainClass with the name of your application class.
Then, provided you have a property for the other view controller, you can call something like:
[appDelegate.viewController someMethod];
And if anyone is wondering how to do this in swift:
if let myDelegate = UIApplication.sharedApplication().delegate as? AppDelegate {
myDelegate.someMethod()
}