枚举

//NS_ENUM，定义状态等普通枚举typedef NS_ENUM(NSUInteger, TTGState) {    TTGStateOK = 0,    TTGStateError,    TTGStateUnknow};//NS_OPTIONS，定义选项typedef NS_OPTIONS(NSUInteger, TTGDirection) {    TTGDirectionNone = 0,    TTGDirectionTop = 1 << 0,    TTGDirectionLeft = 1 << 1,    TTGDirectionRight = 1 << 2,    TTGDirectionBottom = 1 << 3};

转载自：http://tutuge.me/2015/03/21/effective-objective-c-5-enum/?utm_source=tuicool&utm_medium=referral