Swift 计算任意月份天数

func daysCount(year: Int, month: Int) -> Int {
    switch month {
    case 1, 3, 5, 7, 8, 10, 12:
        return 31
    case 4, 6, 9, 11:
        return 30
    case 2:
        let isLeapYear = (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)
        return isLeapYear ? 29 : 28
    default:
        fatalError("非法的月份:\(month)")
    }
}