OC中按位枚举的说明以及用法

OC中枚举类型有两种, 普通枚举和按位枚举

1 普通枚举

typedef NS_ENUM(NSInteger, UIControlContentHorizontalAlignment) {
UIControlContentHorizontalAlignmentCenter = 0,
UIControlContentHorizontalAlignmentLeft   = 1,
UIControlContentHorizontalAlignmentRight  = 2,
UIControlContentHorizontalAlignmentFill   = 3,

};
2 按位枚举

typedef NS_OPTIONS(NSUInteger, UIControlState) {
UIControlStateNormal       = 0,
UIControlStateHighlighted  = 1 << 0,                  // used when UIControl isHighlighted is set
UIControlStateDisabled     = 1 << 1,
UIControlStateSelected     = 1 << 2,                  // flag usable by app (see below)
UIControlStateFocused NS_ENUM_AVAILABLE_IOS(9_0) = 1 << 3, // Applicable only when the screen supports focus
UIControlStateApplication  = 0x00FF0000,              // additional flags available for application use
UIControlStateReserved     = 0xFF000000               // flags reserved for internal framework use

};
3 这个例子可以看出,两种枚举在声明的时候的区别
普通枚举格式

typedef NS_ENUM(枚举值类型, 枚举的名称) {
   枚举值1,//命名规范 枚举的名称+区别词 = 1 << 0或者其他
   枚举值2,
    ...

}
按位枚举格式

typedef NS_OPTIONS(枚举值类型, 枚举的名称) {
 枚举值1,//命名规范 枚举的名称+区别词 = 0或者其他
 枚举值2,
    ...
 }

4 按位枚举的用法

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