详解在Go语言中如何实现枚举类型

const (
   Sunday    = 1
   Tuesday   = 2
   Wednesday = 3
   Thursday  = 4
   Friday    = 5
   Saturday  = 6
   Monday    = 7
)

type WeekDay int

const (
   Sunday    WeekDay = 1
   Tuesday   WeekDay = 2
   Wednesday WeekDay = 3
   Thursday  WeekDay = 4
   Friday    WeekDay = 5
   Saturday  WeekDay = 6
   Monday    WeekDay = 7
)

type WeekDay int

const (
   Sunday WeekDay = iota
   Tuesday
   Wednesday
   Thursday
   Friday
   Saturday
   Monday
)

type WeekDay int

const (
   Sunday WeekDay = iota
   Tuesday
   Wednesday
   Thursday
   Friday
   Saturday
   Monday
)

// Name 返回枚举值的名称
func (w WeekDay) Name() string {
   if w < Sunday || w > Monday {
      return "Unknown"
   }
   return [...]string{"Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"}[w]
}

// Original 由于这个枚举类型的枚举值本质上是整数常量，因此我们可以直接使用枚举值作为它的序号
func (w WeekDay) Original() int {
   return int(w)
}

// 将枚举值转成字符串，便于输出
func (w WeekDay) String() string {
   return w.Name()
}

// Values 返回一个包含所有枚举值的切片
func Values() []WeekDay {
   return []WeekDay{Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday}
}

// ValueOf 使用 switch 语句来根据名称返回对应的枚举值
func ValueOf(name string) (WeekDay, error) {
   switch name {
   case "Sunday":
      return Sunday, nil
   case "Monday":
      return Monday, nil
   case "Tuesday":
      return Tuesday, nil
   case "Wednesday":
      return Wednesday, nil
   case "Thursday":
      return Thursday, nil
   case "Friday":
      return Friday, nil
   case "Saturday":
      return Saturday, nil
   default:
      return 0, fmt.Errorf("invalid WeekDay name: %s", name)
   }
}