swift - 如何获取两个日期之间每个星期五的日期？

Question

我目前使用以下代码返回两个日期之间每一天的日期数组，包括今天的日期和最后一个日期本身。这很好用。

• 但是，我将如何着手修改我已经在做的事情否则命令做同样的事情，而是返回一个日期之间每个星期五的日期数组？例如，如果函数在 2019 年 10 月 23 日星期三被调用以在每个星期五返回，直到 11 月 10 日，第一个日期将是 25 日星期五、11 月 1 日，然后是 11 月 8 日。
• 如果不是每个月的 1 号，我将如何做与上述相同的事情？如果我在 2019 年 10 月 23 日星期三调用该函数以返回每个月的第一天，直到 12 月 16 日。该数组应包含 Nov 1st 和 Dec 1st。

func dates(for date: String) -> [String] {
    // first get the endDate
    guard var endDate = Formatter.date.date(from: date) else { return [] }
    // for calendrical calculations you should use noon time
    endDate = Calendar.current.date(bySettingHour: 12, minute: 0, second: 0, of: endDate)!
    // lets get todays noon time to start
    var date = Calendar.current.date(bySettingHour: 12, minute: 0, second: 0, of: Date())!
    var dates: [String] = []
    // while date less than or equal to end date
    while date <= endDate {
        // add the formatted date to the array
        dates.append( Formatter.date.string(from: date))
        // increment the date by one day
        date = Calendar.current.date(byAdding: .day, value: 1, to: date)!
    }

    return dates
}

Answer 1

你只需要在你的方法中添加一个工作日参数，并在将它添加到你的数组之前检查循环中的日期是否是工作日:

extension Formatter {
    static let date = DateFormatter()
}

---

func dates(for date: String, weekday: Int? = nil) -> [String] {
    Formatter.date.locale = Locale(identifier: "en_US_POSIX")
    Formatter.date.dateFormat = "yyyy-MM-dd"
    // first get the endDate
    guard var endDate = Formatter.date.date(from: date) else { return [] }
    // for calendrical calculations you should use noon time
    endDate = Calendar.current.date(bySettingHour: 12, minute: 0, second: 0, of: endDate)!
    // lets get todays noon time to start
    var date = Calendar.current.date(bySettingHour: 12, minute: 0, second: 0, of: Date())!
    var dates: [String] = []
    // while date less than or equal to end date
    while date <= endDate {
        if weekday == nil {
            dates.append(Formatter.date.string(from: date))
            date = Calendar.current.date(byAdding: .day, value: 1, to: date)!
        } else if let weekday = weekday, Calendar.current.component(.weekday, from: date) == weekday {
            // add the formatted date to the array
            dates.append(Formatter.date.string(from: date))
            date = Calendar.current.date(byAdding: .weekOfYear, value: 1, to: date)!
        } else {
            date = Calendar.current.date(byAdding: .day, value: 1, to: date)!
        }
    }
    return dates
}

---

dates(for: "2019-12-25")  // ["2019-10-23", "2019-10-24", "2019-10-25", "2019-10-26", "2019-10-27", "2019-10-28", "2019-10-29", "2019-10-30", "2019-10-31", "2019-11-01", "2019-11-02", "2019-11-03", "2019-11-04", "2019-11-05", "2019-11-06", "2019-11-07", "2019-11-08", "2019-11-09", "2019-11-10", "2019-11-11", "2019-11-12", "2019-11-13", "2019-11-14", "2019-11-15", "2019-11-16", "2019-11-17", "2019-11-18", "2019-11-19", "2019-11-20", "2019-11-21", "2019-11-22", "2019-11-23", "2019-11-24", "2019-11-25", "2019-11-26", "2019-11-27", "2019-11-28", "2019-11-29", "2019-11-30", "2019-12-01", "2019-12-02", "2019-12-03", "2019-12-04", "2019-12-05", "2019-12-06", "2019-12-07", "2019-12-08", "2019-12-09", "2019-12-10", "2019-12-11", "2019-12-12", "2019-12-13", "2019-12-14", "2019-12-15", "2019-12-16", "2019-12-17", "2019-12-18", "2019-12-19", "2019-12-20", "2019-12-21", "2019-12-22", "2019-12-23", "2019-12-24", "2019-12-25"]
dates(for: "2019-12-25", weekday: 6) // ["2019-10-25", "2019-11-01", "2019-11-08", "2019-11-15", "2019-11-22", "2019-11-29", "2019-12-06", "2019-12-13", "2019-12-20"]

---

func firstDayOfTheMonth(until date: String) -> [String] {
    Formatter.date.locale = Locale(identifier: "en_US_POSIX")
    Formatter.date.dateFormat = "yyyy-MM-dd"
    guard let endDate = Formatter.date.date(from: date) else { return [] }
    var date = Date()
    var dates: [String] = []
    // while date less than or equal to end date
    while let firstDayOfTheMonth = Calendar.current.nextDate(after: date, matching: .init(day: 1), matchingPolicy: .nextTime), firstDayOfTheMonth <= endDate {
        dates.append(Formatter.date.string(from: firstDayOfTheMonth))
        date = firstDayOfTheMonth
    }
    return dates
}

---

firstDayOfTheMonth(until: "2019-12-25")  // ["2019-11-01", "2019-12-01"]