问题
I saw a few examples about adding observer and handle in the same class, but what I want to know is if it's possible to add observer in first view controller and handle it in second view controller?
I want constantly send distance from first view controller and handle it in the 2nd one.
The 2nd view controller added as a sub view: addSubview, addChildViewController.
It's something like broadcast in android.
回答1:
Yes it is possible. NSNotificationCenter works exactly in that way.
Firstly, you will have to register the listener in the first view controller as below.
-(void)viewDidLoad
{
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(somethingHappens:) name:@"notificationName" object:nil];
}
-(void)somethingHappens:(NSNotification*)notification
{
}
Secondly, post the notification from the second view controller as below.
[[NSNotificationCenter defaultCenter] postNotificationName:@"notificationName" object:obj];
The system will broadcast the notification to all the listeners.
回答2:
There is another way to do this (in case you want to let other view controllers know if a value of an object has changed). You can use KVO (Key-Value Observing): http://developer.apple.com/library/ios/#documentation/cocoa/conceptual/KeyValueObserving/Articles/KVOBasics.html
来源：https://stackoverflow.com/questions/17080605/add-addobserver-nsnotificationcenter-in-a-1st-view-controller-handle-in-2n