枚举enum——三种声明语法

enum BlenderSpeed {
    BlenderSpeedStir = 1,
    BlenderSpeedChop = 2,
    BlenderSpeedLiquify = 5,
    BlenderSpeedPulse = 9,
    BlenderSpeedIceCrush = 15
};

typedef enum {
    BlenderSpeedStir2 = 1,
    BlenderSpeedChop2 = 2,
    BlenderSpeedLiquify2 = 5,
    BlenderSpeedPulse2 = 9,
    BlenderSpeedIceCrush2 = 15
} BlenderSpeed2;

//NS_ENUM()实际上是一个预处理器宏，带有两个实参： 数据类型和名字
typedef NS_ENUM(int, BlenderSpeed3) {
    BlenderSpeedStir3,
    BlenderSpeedChop3,
    BlenderSpeedLiquify3,
    BlenderSpeedPulse3,
    BlenderSpeedIceCrush3
};