一荣茫、枚舉類型想帅、enum
枚舉類型
ypedef NS_ENUM(NSInteger, UIViewAnimationTransition) {
UIViewAnimationTransitionNone,//默認(rèn)從0開始
UIViewAnimationTransitionFlipFromLeft,
UIViewAnimationTransitionFlipFromRight,
UIViewAnimationTransitionCurlUp,
UIViewAnimationTransitionCurlDown,
};
typedef NS_OPTIONS(NSUInteger, UIViewAutoresizing) {
UIViewAutoresizingNone = 0,
UIViewAutoresizingFlexibleLeftMargin = 1 << 0,
UIViewAutoresizingFlexibleWidth = 1 << 1,
UIViewAutoresizingFlexibleRightMargin = 1 << 2,
UIViewAutoresizingFlexibleTopMargin = 1 << 3,
UIViewAutoresizingFlexibleHeight = 1 << 4,
UIViewAutoresizingFlexibleBottomMargin = 1 << 5
};
從枚舉定義來看，NS_ENUM和NS_OPTIONS本質(zhì)是一樣的啡莉，僅僅從字面上來區(qū)分其用途港准。NS_ENUM是通用情況，NS_OPTIONS一般用來定義具有位移操作或特點(diǎn)的情況（bitmask)咧欣，也適用于可以同時(shí)選擇多個(gè)選項(xiàng)的情況浅缸。
