NS_OPTIONS枚举的用法

定义:

```objective-c
//NS_OPTIONS，定义选项
typedef NS_OPTIONS(NSUInteger, MyOption) {
MyOptionNone = 0, //二进制0000,十进制0
MyOption1 = 1 << 0,//0001,1
MyOption2 = 1 << 1,//0010,2
MyOption3 = 1 << 2,//0100,4
MyOption4 = 1 << 3,//1000,8
};

##使用:

```objective-c
//声明定义枚举变量
MyOption option = MyOption1 | MyOption2;//0001 | 0010 = 0011,3

//检查是否包含某选型
if ( option & MyOption3 ){ //0011 & 0100 = 0000
     //包含MyOption3
}else{
     //不包含MyOption3
}

//增加选项:
option = option | MyOption4;//0011 | 1000 = 1011, 11
//减少选项
option = option & (~MyOption4);//1011 & (~1000) = 1011 & 0111 = 0011, 3