使用 DateComponents 创建日期

Question

我想得到一周的第一天和最后一天。但我的结果与苹果的文档不符： https://developer.apple.com/documentation/foundation/nsdatecomponents/1410442-weekday

这是我的功能：

func startAndEndDateOfWeek(weekOfYearWithYear: (week: Int,year: Int)) -> (start: Date, end: Date) {
    var output = (start: Date.init(), end: Date.init())

    let calendar = Calendar(identifier: .gregorian)
    var firstDayComponents = DateComponents()
    firstDayComponents.weekOfYear = weekOfYearWithYear.week
    firstDayComponents.yearForWeekOfYear = weekOfYearWithYear.year
    firstDayComponents.weekday = 1

    let firstDay = calendar.date(from: firstDayComponents)

    var lastDayComponents = DateComponents()
    lastDayComponents.weekOfYear = weekOfYearWithYear.week
    lastDayComponents.yearForWeekOfYear = weekOfYearWithYear.year
    lastDayComponents.weekday = 2

    let lastDay = calendar.date(from: lastDayComponents)
    output = (start: firstDay!, end: lastDay!)
    return output
}

.weekday = 2 -> 导致星期日而不是 0.

我也想拥有一整天而不是16:00。

Answer 1

一些观察：

在公历中，weekday = 1表示星期日； weekday = 2 表示星期一；等。您可以查看 calendar.maximumRange(of: .weekday) 以获得有效值的范围，您可以查看 calendar.weekdaySymbols 以了解这些 weekDay 值的含义（例如“Sun”、“Mon”、 “星期二”、“星期三”、“星期四”、“星期五”和“星期六”）。

你说：

I also want to have the entire day and not 16:00.

一个Date对象引用了一个时间点。所以它不能代表“一整天”。但它可以代表午夜（而您所在时区的午夜可能是 GMT/UTC/Zulu 的下午 4 点）。

您也可以 return 一个 DateInterval，它代表一个时间范围。

func interval(ofWeek week: Int, in year: Int) -> DateInterval {
    let calendar = Calendar.current

    let date = DateComponents(calendar: calendar, weekOfYear: week, yearForWeekOfYear: year).date!
    return calendar.dateInterval(of: .weekOfYear, for: date)!
}

然后

let formatter = DateIntervalFormatter()
formatter.dateStyle = .short
formatter.timeStyle = .short

let year = Calendar.current.component(.year, from: Date())
let dateInterval = interval(ofWeek: 2, in: year)
print(formatter.string(from: dateInterval))

在美国地区，间隔从 1 月 6 日开始：

1/6/19, 12:00 AM – 1/13/19, 12:00 AM

而在德语地区，间隔从 7 日开始：

07.01.19, 00:00 – 14.01.19, 00:00

如果你想要一周的第一天和一周的最后一天的开始，你可以这样做：

func startAndEndDate(ofWeek week: Int, in year: Int) -> (Date, Date) {
    let date = DateComponents(calendar: calendar, weekOfYear: week, yearForWeekOfYear: year).date!
    let lastDate = calendar.date(byAdding: .day, value: 6, to: date)!

    return (date, lastDate)
}

然后

let formatter = DateFormatter()
formatter.dateStyle = .short

let year = Calendar.current.component(.year, from: Date())
let (start, end) = startAndEndDate(ofWeek: 2, in: year)
print(formatter.string(from: start), "-", formatter.string(from: end))

使用 DateComponents 创建日期

Creating a date with DateComponents

calendar

nsdatecomponents

swift