Adding an observer to each view or present view dynamically - iphone

Question

I am posting a notification locally in the app when ever I receive a remote notification.
- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
{
NSLog(#"Received notification: %#", userInfo);
[[NSNotificationCenter defaultCenter] postNotificationName:#"NEWMESSAGE" object:nil userInfo:userInfo]; }
I have added an observer to the view in the function viewWillAppear() and remove the observer in viewWillDisappear().
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(newMessageReceived:) name:#"NEWMESSAGE" object:nil];
and
[[NSNotificationCenter defaultCenter] removeObserver:self];
My question is I want to override every viewWillAppear and viewWillDisappear functions in all *.m files that use these functions in my app.
or how can I dynamically add an observer (like above) to the present view and remove the observer when that view disappears. it should be like a global action whenever view changes observer to be added and removed when it changes again.
Is this possible? if so please guide me.
thanks in advance.

Answer 1

Some thoughts:
You can subclass UIViewController and implement these method in the subclass-ed view controller class. Then you need to create all your views as the subclass of this UIViewController.
Example:
//Creating a custom subclass of UIViewController
#interface CustomViewController : UIViewController
#end
#implementation CustomViewController
- (void)viewWillAppear:(BOOL)animated
{
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(newMessageReceived:) name:#"NEWMESSAGE" object:nil];
}
- (void)viewWillDisappear:(BOOL)animated
{
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
#end
And create all your view controller as the subclass of CustomViewController.