iOS 9开始, 使用
- removeObserver: Removes all entries specifying a given observer from the notification center's dispatch table. Declaration - (void)removeObserver:(id)observer; Parameters observer The observer to remove. Discussion If your app targets iOS 9.0 and later or macOS 10.11 and later, you don't need to unregister an observer in its dealloc method. Otherwise, you should call this method or removeObserver:name:object: before observer or any object specified in addObserverForName:object:queue:usingBlock: or addObserver:selector:name:object: is deallocated. You shouldn't use this method to remove all observers from a long-lived object, because your code may not be the only code adding observers that involve the object. The following example illustrates how to unregister someObserver for all notifications for which it had previously registered. This is safe to do in the dealloc method, but should not otherwise be used (use removeObserver:name:object: instead). [[NSNotificationCenter defaultCenter] removeObserver:someObserver]; Availability iOS 2.0+ macOS 10.0+ tvOS 9.0+ watchOS 2.0+ See Also removeObserver:name:object:
iOS9之前, scrollView的delegate是没有用weak修饰的, 需要手动释放.
//iOS9 以前 @property(nonatomic,unsafe_unretain) id<UIScrollViewDelegate> delegate; //iOS9 @property(nullable,nonatomic,weak) id<UIScrollViewDelegate> delegate;