NS_AVAILABLE_IOS与NS_DEPRECATED_I

在iOS的API中，我们经常会看到

// Returns interface orientation masks.
- (UIInterfaceOrientation)preferredInterfaceOrientationForPresentation NS_AVAILABLE_IOS(6_0) __TVOS_PROHIBITED;

// The rotating header and footer views will slide out during the rotation and back in once it has completed.
- (nullable UIView *)rotatingHeaderView NS_DEPRECATED_IOS(2_0,8_0, "Header views are animated along with the rest of the view hierarchy") __TVOS_PROHIBITED;     // Must be in the view hierarchy. Default returns nil.
- (nullable UIView *)rotatingFooterView NS_DEPRECATED_IOS(2_0,8_0, "Footer views are animated along with the rest of the view hierarchy") __TVOS_PROHIBITED;     // Must be in the view hierarchy. Default returns nil.

@property(nonatomic,readonly) UIInterfaceOrientation interfaceOrientation NS_DEPRECATED_IOS(2_0,8_0) __TVOS_PROHIBITED;

// Notifies when rotation begins, reaches halfway point and ends.
- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration NS_DEPRECATED_IOS(2_0,8_0, "Implement viewWillTransitionToSize:withTransitionCoordinator: instead") __TVOS_PROHIBITED;
- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation NS_DEPRECATED_IOS(2_0,8_0) __TVOS_PROHIBITED;

其含义分别为：NS_AVAILABEL_IOS(6_0)表示，自IOS6.0开始支持该方法，若在IOS6.0之前的版本使用该函数，则会导致 Crash；NS_DEPRECATED_IOS(2_0,3_0)表示该函数只能在IOS2.0 和 IOS3.0之间使用，是已被废弃的函数，但并不是说在IOS3.0之后不能使用该函数，是可以使用，但也需要考虑找其他替代方法了
另外，还有 NS_DEPRECATED(10_6,10_9,2_0,7_0)这种写法，为自mac10.6和ios2.0引入，在mac10.9和ios7.0被废弃

参考文章：http://blog.csdn.net/sanjiewang/article/details/38559909