How to use a ViewController as a AppDelegate? - objective-c

Question

I made a book for children. Every page is a ViewController. In the beginning, I did all the switching of the ViewControllers in the AppDelegate, but after having troubles with AutoRotation i did all the switching in another ViewController called ViewControllerSwitch.
Before, the code was like this. In the AppDelegate:
- (void)goToNextPage3 {
self.view3 = [[[ViewController3 alloc] init] autorelease];
view3.view.frame = CGRectMake(769, 0, 768, 1024);
[window addSubview:view3.view];
[UIView …SomeAnimationStuff...];  
[UIView setAnimationDidStopSelector:#selector(animationDidStop3:finished:context:)];
}
 - (void)animationDidStop3:(NSString *)animationID finished:(NSNumber *)finished context: (void *)context {
[self.view1a.view removeFromSuperview];
self.view1a = nil;
}
And here is the code from one of my view controllers ("pages") called ViewController1a:
- (void)buttonClicked {
MyBookAppDelegate* next2 =(MyBookAppDelegate *) [[UIApplication sharedApplication] delegate];
[next2 goToNextPage3];
}
This worked like a charm.
Now all my switching is in ViewControllerSwitch. How should I change the code in ViewController1a to access goToNextPage3?
I tried this:
- (void)buttonClicked {
ViewControllerSwitch* next2 = (ViewControllerSwitch *) [[UIApplication sharedApplication] delegate];
[next2 goToNextPage3];
}
It gives me a SIGABRT at [next2 goToNextPage3].
Any ideas?
Update:
i am still trying, so now i did this:
in my Viewcontroller1a.h:
#import <UIKit/UIKit.h>
#import "ViewControllerSwitch.h"
#class ViewController2;
#class ViewControllerSwitch;
#protocol ViewController1Delegate;
#interface ViewController1a : UIViewController
{
id<ViewController1aDelegate>myDelegate;
}
#property(nonatomic, assign)id<ViewController1Delegate>myDelegate;
#end
#protocol ViewController1Delegate
-(void)goToNextPageV;
#end
and in my .m file:
- (void)buttonClicked {
[self.myDelegate goToNextPageV];
}
i know there is something missing in the ViewControllerSwitch but i don´t know what.

Answer 1

As LordTwaroog said, this line is returning an object (your app delegate) of type MyBookAppDelegate:
[[UIApplication sharedApplication] delegate];
Then you're attempting to cast it to be an object of type ViewControllerSwitch with this:
(ViewControllerSwitch *)
This is incorrect. Your app delegate is an NSObject subclass conforming to the UIApplicationDelegate protocol. It's not a view controller.
The correct code might look like this:
- (void)buttonClicked {
ViewControllerSwitch* next2 = [ViewControllerSwitch alloc] initWithNibName:#"ViewControllerSwitch" bundle:nil]
[next2 goToNextPage3];
}
But depending on your app structure this might not be what you want. This is creating a brand new object of type ViewControllerSwitch. It's not returning the possibly-already-existing other ViewControllerSwitch object.
When you were using the app delegate to perform the switching, you had the benefit of being able to retrieve the existing app delegate object (rather than retrieving a newly created object of it's type). The app delegate is a singleton object, easily retrieved by calling [[UIApplication sharedApplication] delegate]. However, your ViewControllerSwitch object might not be set up as a singleton. So your access to it will depend on your object ownership structure. We'd have to see more of your code to help you with that.

Answer 2

[[UIApplication sharedApplication] delegate] still returns MyBookAppDelegate. Why do you try to get ViewControllerSwitch object out of it? You should use your ViewControllerSwitch object. Can you provide more code details on this object?
Possible solutions (if I understand you well):
Put your ViewControllerSwitch as an object in AppDelegate, so you could use:
ViewControllerSwitch *switch = [[[UIApplication sharedApplication] delegate] viewControllerSwitch]
Each ViewController can have a reference to your ViewControllerSwitch
Each ViewController should have a delegate with protocol (e.g.) ViewControllerDelegate, which will have a method to perform switching. Then after setting the delegate to appropriate object, you'll be able to switch your pages