吐槽下iOS8[一] notification, scrollview.delegate

NotificationCenter

从iOS 9开始, 使用NotificationCenter添加Observer之后, 不在需要自行调用removeObserver:方法:

- 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:

scrollView.delegate

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;

这里还有更加详细的说明:

https://www.jianshu.com/p/19bfa3b6c06d