flagx

Usage

Assume that you have the following Date type.

type Date struct {
  Year, Month, Day int
}

Configure Parse and String function to use flags of type Date.

var dateFlag = flagx.Config[Date]{
  Parse: func(s string) (Date, error) {
    tm, err := time.Parse("2006-01-02", s)
    if err != nil {
      return Date{}, err
    }
    year, month, day := tm.Date()
    return Date{Year: year, Month: int(month), Day: day}, nil
  },
  String: func(d Date) string {
    return fmt.Sprintf("%04d-%02d-%02d", d.Year, d.Month, d.Day)
  },
}

Now you can use dateFlag.Value() to create flag.Value, which can be used for flag.Var().

var date Date

func init() {
  flag.Var(dateFlag.Value(&date, Date{Year: 2006, Month: 1, Day: 2}), "date", "usage")
}