枚举NS_OPTIONS与NS_ENUM

NS_ENUM

typedef NS_ENUM(int,Banner){
      banner_Init =0, //启动页  0
      banner_Home, //首页1
      banner_FindJob, //找工作2
      banner_train ,//培训3
      banner_Shopping, //商城4
};

大括号中的枚举项的值可自定义，若是定义了枚举项其中一项的值后面依次在它的前一项的值上加1

NS_OPTIONS

typedef NS_OPTIONS(NSUInteger, UISwipeGestureRecognizerDirection) {
    UISwipeGestureRecognizerDirectionNone = 0,  //值为0
    UISwipeGestureRecognizerDirectionRight = 1 << 0,  //值为2的0次方
    UISwipeGestureRecognizerDirectionLeft = 1 << 1,  //值为2的1次方
    UISwipeGestureRecognizerDirectionUp = 1 << 2,  //值为2的2次方
    UISwipeGestureRecognizerDirectionDown = 1 << 3  //值为2的3次方
};

    位移枚举即是在你需要的地方可以同时存在多个枚举值如这样：

    UISwipeGestureRecognizer *swipeGR = [[UISwipeGestureRecognizer alloc] init];
    swipeGR.direction = UISwipeGestureRecognizerDirectionDown | UISwipeGestureRecognizerDirectionLeft | UISwipeGestureRecognizerDirectionRight;
    //这里几个枚举项同时存在表示它的方向同时包含1.向下2.向左3.向右

    而NS_ENUM定义的枚举不能几个枚举项同时存在，只能选择其中一项，像这样：

    NSMutableParagraphStyle *paragraph = [[NSMutableParagraphStyle alloc] init];
    paragraph.baseWritingDirection = NSWritingDirectionNatural;