Enum 枚举

/* Values for NSTextAlignment */
typedef NS_ENUM(NSInteger, NSTextAlignment) {
    NSTextAlignmentLeft      = 0,    // Visually left aligned
#if TARGET_OS_IPHONE
    NSTextAlignmentCenter    = 1,    // Visually centered
    NSTextAlignmentRight     = 2,    // Visually right aligned
#else /* !TARGET_OS_IPHONE */
    NSTextAlignmentRight     = 1,    // Visually right aligned
    NSTextAlignmentCenter    = 2,    // Visually centered
#endif
    NSTextAlignmentJustified = 3,    // Fully-justified. The last line in a paragraph is natural-aligned.
    NSTextAlignmentNatural   = 4,    // Indicates the default alignment for script
} NS_ENUM_AVAILABLE_IOS(6_0);