使用NSDate获取星期几

时间：2014-08-27 17:10:57

标签： swift nsdate nscalendar

我创建了一个方法，该方法应该在＆＃34; YYYY-MM-DD＆＃34;形成并吐出一个int，表示与其所在周相关的日期位置（无论它在几个月之间是否重叠）。所以例如星期日= 1星期一= 2，依此类推。

这是我的代码：

    func getDayOfWeek(today:String)->Int{

    var formatter:NSDateFormatter = NSDateFormatter()
    formatter.dateFormat = "YYYY-MM-DD"
    var todayDate:NSDate = formatter.dateFromString(today)!
    var myCalendar:NSCalendar = NSCalendar(calendarIdentifier: NSGregorianCalendar)
    var myComponents = myCalendar.components(NSCalendarUnit.WeekdayOrdinalCalendarUnit, fromDate: todayDate)
    var weekDay = myComponents.weekdayOrdinal
    return weekDay
}

我知道NSCalendarUnit.WeekdayOrdinalCalendar是错误的，但我尝试过我认为最合乎逻辑的组合。并且还使用了myComponents.weekdayOrdinal，例如mycomponents.day或.weekday。

以下是我可以使用的选项：

static var EraCalendarUnit: NSCalendarUnit { get }
static var YearCalendarUnit: NSCalendarUnit { get }
static var MonthCalendarUnit: NSCalendarUnit { get }
static var DayCalendarUnit: NSCalendarUnit { get }
static var HourCalendarUnit: NSCalendarUnit { get }
static var MinuteCalendarUnit: NSCalendarUnit { get }
static var SecondCalendarUnit: NSCalendarUnit { get }
static var WeekCalendarUnit: NSCalendarUnit { get }
static var WeekdayCalendarUnit: NSCalendarUnit { get }
static var WeekdayOrdinalCalendarUnit: NSCalendarUnit { get }
static var QuarterCalendarUnit: NSCalendarUnit { get }
static var WeekOfMonthCalendarUnit: NSCalendarUnit { get }
static var WeekOfYearCalendarUnit: NSCalendarUnit { get }
static var YearForWeekOfYearCalendarUnit: NSCalendarUnit { get }
static var CalendarCalendarUnit: NSCalendarUnit { get }
static var TimeZoneCalendarUnit: NSCalendarUnit { get }

我不清楚，因为没有DayOfWeekUnit选项（或类似的东西）。

19 个答案:

答案 0 :(得分：116)

Swift 3＆amp; 4

在Swift 3中，检索星期几的数字会大大简化，因为DateComponents不再是可选的。这是一个扩展名：

extension Date {
    func dayNumberOfWeek() -> Int? {
        return Calendar.current.dateComponents([.weekday], from: self).weekday 
    }
}

// returns an integer from 1 - 7, with 1 being Sunday and 7 being Saturday
print(Date().dayNumberOfWeek()!) // 4

如果您正在寻找星期几的书面本地化版本：

extension Date {
    func dayOfWeek() -> String? {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "EEEE"
        return dateFormatter.string(from: self).capitalized 
        // or use capitalized(with: locale) if you want
    }
}

print(Date().dayOfWeek()!) // Wednesday

答案 1 :(得分：105)

您正在寻找的内容（如果我理解正确的话）是NSCalendarUnit.CalendarUnitWeekday。 NSDateComponents的相应属性为weekday。

另请注意您的日期格式错误（ 完整规范可以在这里找到：http://unicode.org/reports/tr35/tr35-6.html）。

使用自动类型推断可以略微简化函数，在常量足够的情况下也可以使用很多变量。 此外，该函数应返回一个可选的nil 输入无效的字符串。

更新了 Swift 3及更高版本的代码： 

func getDayOfWeek(_ today:String) -> Int? {
    let formatter  = DateFormatter()
    formatter.dateFormat = "yyyy-MM-dd"
    guard let todayDate = formatter.date(from: today) else { return nil }
    let myCalendar = Calendar(identifier: .gregorian)
    let weekDay = myCalendar.component(.weekday, from: todayDate)
    return weekDay
}

示例：的

if let weekday = getDayOfWeek("2014-08-27") {
    print(weekday)
} else {
    print("bad input")
}

Swift 2的原始答案 

func getDayOfWeek(today:String)->Int? {

    let formatter  = NSDateFormatter()
    formatter.dateFormat = "yyyy-MM-dd"
    if let todayDate = formatter.dateFromString(today) {
        let myCalendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)!
        let myComponents = myCalendar.components(.Weekday, fromDate: todayDate)
        let weekDay = myComponents.weekday
        return weekDay
    } else {
        return nil
    }
}

答案 2 :(得分：27)

如果你想要完整的“星期日”，“星期一”，“星期二”，“星期三”等等。

编辑：实际上有一种内置格式可以返回本地化的日期名称：

extension NSDate {
    func dayOfTheWeek() -> String? {        
        let dateFormatter = NSDateFormatter()
        dateFormatter.dateFormat = "EEEE"
        return dateFormatter.stringFromDate(self)
    }
}

我之前的解决方案（仅限英文）：

extension NSDate {

    func dayOfTheWeek() -> String? {
        let weekdays = [
            "Sunday",
            "Monday",
            "Tuesday",
            "Wednesday",
            "Thursday",
            "Friday",
            "Saturday"
        ]

        let calendar: NSCalendar = NSCalendar.currentCalendar()
        let components: NSDateComponents = calendar.components(.Weekday, fromDate: self)
        return weekdays[components.weekday - 1]
    }
}

您不需要打开日历和组件，它们由基础框架保证。

用法：

print(myDate.dayOfTheWeek())

答案 3 :(得分：16)

简单的回答（swift 3）：

Calendar.current.component(.weekday, from: Date())

答案 4 :(得分：10)

在我的情况下，我每天都用三个字母的字符串。我修改了@Martin R＆＃39的功能如下：

func getDayOfWeekString(today:String)->String? {
    let formatter  = NSDateFormatter()
    formatter.dateFormat = "yyyy-MM-dd"
    if let todayDate = formatter.dateFromString(today) {
        let myCalendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)!
        let myComponents = myCalendar.components(.Weekday, fromDate: todayDate)
        let weekDay = myComponents.weekday
        switch weekDay {
        case 1:
            return "Sun"
        case 2:
            return "Mon"
        case 3:
            return "Tue"
        case 4:
            return "Wed"
        case 5:
            return "Thu"
        case 6:
            return "Fri"
        case 7:
            return "Sat"
        default:
            print("Error fetching days")
            return "Day"
        }
    } else {
        return nil
    }
}

答案 5 :(得分：10)

有一种更简单的方法。只需将您的字符串日期传递给以下函数，它将为您提供日期名称：）

func getDayNameBy(stringDate: String) -> String
    {
        let df  = NSDateFormatter()
        df.dateFormat = "YYYY-MM-dd"
        let date = df.dateFromString(stringDate)!
        df.dateFormat = "EEEE"
        return df.stringFromDate(date);
    }

答案 6 :(得分：8)

Swift 3日期延期 

extension Date {
    var weekdayOrdinal: Int {
        return Calendar.current.component(.weekday, from: self)
    }
}

答案 7 :(得分：4)

您可以使用此表date_formats 用于将日期转换为不同的格式。我最短的代码：

func getDayOfWeek(today: String) -> Int{
    let formatter:NSDateFormatter = NSDateFormatter()
    formatter.dateFormat = "yyyy-MM-dd"
    let todayDate = formatter.dateFromString(today)
    formatter.dateFormat = "e" // "eeee" -> Friday
    let weekDay = formatter.stringFromDate(todayDate!)
    return Int(weekDay)!
}
getDayOfWeek("2015-12-18") // 6

答案 8 :(得分：3)

extension Date {

var weekdayName: String {
    let formatter = DateFormatter(); formatter.dateFormat = "E"
    return formatter.string(from: self as Date)
}

var weekdayNameFull: String {
    let formatter = DateFormatter(); formatter.dateFormat = "EEEE"
    return formatter.string(from: self as Date)
}
var monthName: String {
    let formatter = DateFormatter(); formatter.dateFormat = "MMM"
    return formatter.string(from: self as Date)
}
var OnlyYear: String {
    let formatter = DateFormatter(); formatter.dateFormat = "YYYY"
    return formatter.string(from: self as Date)
}
var period: String {
    let formatter = DateFormatter(); formatter.dateFormat = "a"
    return formatter.string(from: self as Date)
}
var timeOnly: String {
    let formatter = DateFormatter(); formatter.dateFormat = "hh : mm"
    return formatter.string(from: self as Date)
}
var timeWithPeriod: String {
    let formatter = DateFormatter(); formatter.dateFormat = "hh : mm a"
    return formatter.string(from: self as Date)
}

var DatewithMonth: String {
    let formatter = DateFormatter(); formatter.dateStyle = .medium ;        return formatter.string(from: self as Date)
}
}

使用 让工作日= Date（）。weekdayName

答案 9 :(得分：2)

实用的解决方案......

请注意，结果是整数1到7。

（不是零至六。）

let trivialDayStringsORDINAL = ["", "SUN","MON","TUE","WED","THU","FRI","SAT"]
// note that zero is not used

然后...... 

let dow = Calendar.current.component(.weekday, from: someDate)
print( trivialDayStringsORDINAL[dow] )

答案 10 :(得分：1)

我最终需要从日期开始输入更多字符串，包括一周中的日期（例如＆＃34;第五和第34;）和一年中的一个月（例如八月）。以下是我根据@Martin R函数创建的所有三个函数，并修改为返回3个char字符串：

//Date String Helper Functions
func getDayOfWeek(today:String)->String? {
    let formatter  = NSDateFormatter()
    formatter.dateFormat = "yyyy-MM-dd"
    if let todayDate = formatter.dateFromString(today) {
        let myCalendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)!
        let myComponents = myCalendar.components(.Weekday, fromDate: todayDate)
        let weekDay = myComponents.weekday
        switch weekDay {
        case 1:
            return "Sun"
        case 2:
            return "Mon"
        case 3:
            return "Tue"
        case 4:
            return "Wed"
        case 5:
            return "Thu"
        case 6:
            return "Fri"
        case 7:
            return "Sat"
        default:
            print("Error fetching days")
            return "Day"
        }
    } else {
        return nil
    }
}

func getDateOfMonth(today:String)->String? {
    let formatter  = NSDateFormatter()
    formatter.dateFormat = "yyyy-MM-dd"
    if let todayDate = formatter.dateFromString(today) {
        let myCalendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)!
        let myComponents = myCalendar.components(.Day, fromDate: todayDate)
        let weekDay = myComponents.day
        switch weekDay {
        case 1:
            return "1st"
        case 2:
            return "2nd"
        case 3:
            return "3rd"
        case 4:
            return "4th"
        case 5:
            return "5th"
        case 6:
            return "6th"
        case 7:
            return "7th"
        case 8:
            return "8th"
        case 9:
            return "9th"
        case 10:
            return "10th"
        case 11:
            return "11th"
        case 12:
            return "12th"
        case 13:
            return "13th"
        case 14:
            return "14th"
        case 15:
            return "15th"
        case 16:
            return "16th"
        case 17:
            return "17th"
        case 18:
            return "18th"
        case 19:
            return "19th"
        case 20:
            return "20th"
        case 21:
            return "21st"
        case 22:
            return "22nd"
        case 23:
            return "23rd"
        case 24:
            return "24th"
        case 25:
            return "25th"
        case 26:
            return "26th"
        case 27:
            return "27th"
        case 28:
            return "28th"
        case 29:
            return "29th"
        case 30:
            return "30th"
        case 31:
            return "31st"
        default:
            print("Error fetching Date Of Month")
            return "Day"
        }
    } else {
        return nil
    }
}

func getMonthOfYear(today:String)->String? {
    let formatter  = NSDateFormatter()
    formatter.dateFormat = "yyyy-MM-dd"
    if let todayDate = formatter.dateFromString(today) {
        let myCalendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)!
        let myComponents = myCalendar.components(.Month, fromDate: todayDate)
        let month = myComponents.month
        switch month {
        case 1:
            return "Jan"
        case 2:
            return "Feb"
        case 3:
            return "Mar"
        case 4:
            return "Apr"
        case 5:
            return "May"
        case 6:
            return "Jun"
        case 7:
            return "Jul"
        case 8:
            return "Aug"
        case 9:
            return "Sep"
        case 10:
            return "Oct"
        case 11:
            return "Nov"
        case 12:
            return "Dec"
        default:
            print("Error fetching months")
            return "Month"
        }
    } else {
        return nil
    }
}

答案 11 :(得分：1)

SWIFT 2.0代码，用于显示从星期一开始的当前周。

@IBAction func show（sender：AnyObject）{

   // Getting Days of week corresponding to their dateFormat

    let calendar = NSCalendar.currentCalendar()
    let dayInt: Int!
    var weekDate: [String] = []
    var i = 2

    print("Dates corresponding to days are")
    while((dayInt - dayInt) + i < 9)
    {
        let weekFirstDate = calendar.dateByAddingUnit(.Day, value: (-dayInt+i), toDate: NSDate(), options: [])
        let dateFormatter = NSDateFormatter()
        dateFormatter.dateFormat = "EEEE dd MMMM"
        let dayOfWeekString = dateFormatter.stringFromDate(weekFirstDate!)
        weekDate.append(dayOfWeekString)
        i++
    }
    for i in weekDate
    {
        print(i) //Printing the day stored in array
    }
}

// function to get week day
func getDayOfWeek(today:String)->Int {

    let formatter  = NSDateFormatter()
    formatter.dateFormat = "MMM-dd-yyyy"
    let todayDate = formatter.dateFromString(today)!
    let myCalendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)!
    let myComponents = myCalendar.components(.Weekday, fromDate: todayDate)
    let weekDay = myComponents.weekday
    return weekDay
}


@IBAction func DateTitle(sender: AnyObject) {


    // Getting currentDate and weekDay corresponding to it
    let currentDate = NSDate()
    let dateFormatter = NSDateFormatter()
    dateFormatter.dateFormat = "MMM-dd-yyyy"
    let dayOfWeekStrings = dateFormatter.stringFromDate(currentDate)
    dayInt = getDayOfWeek(dayOfWeekStrings)

}

答案 12 :(得分：1)

此代码用于查找整个当前周。它是用Swift 2.0编写的：

var i = 2
var weekday: [String] = []
var weekdate: [String] = []
var weekmonth: [String] = []

@IBAction func buttonaction(sender: AnyObject) {

    let currentDate = NSDate()
    let dateFormatter = NSDateFormatter()
    dateFormatter.dateFormat = "MMM-dd-yyyy"
    let dayOfWeekStrings = dateFormatter.stringFromDate(currentDate)
    let weekdays = getDayOfWeek(dayOfWeekStrings)
    let calendar = NSCalendar.currentCalendar()

    while((weekdays - weekdays) + i < 9)
    {
        let weekFirstDate = calendar.dateByAddingUnit(.Day, value: (-weekdays+i), toDate: NSDate(), options: [])

        let dayFormatter = NSDateFormatter()
        dayFormatter.dateFormat = "EEEE"
        let dayOfWeekString = dayFormatter.stringFromDate(weekFirstDate!)
        weekday.append(dayOfWeekString)

        let dateFormatter = NSDateFormatter()
        dateFormatter.dateFormat = "dd"
        let dateOfWeekString = dateFormatter.stringFromDate(weekFirstDate!)
        weekdate.append(dateOfWeekString)

        let monthFormatter = NSDateFormatter()
        monthFormatter.dateFormat = "MMMM"
        let monthOfWeekString = monthFormatter.stringFromDate(weekFirstDate!)
        weekmonth.append(monthOfWeekString)

        i++
    }

    for(var j = 0; j<7 ; j++)
    {
    let day = weekday[j]
    let date = weekdate[j]
    let month = weekmonth[j]
    var wholeweek = date + "-" + month + "(" + day + ")"
    print(wholeweek)
    }

}

func getDayOfWeek(today:String)->Int {
    let formatter  = NSDateFormatter()
    formatter.dateFormat = "MMM-dd-yyyy"
    let todayDate = formatter.dateFromString(today)!
    let myCalendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)!
    let myComponents = myCalendar.components(.Weekday, fromDate: todayDate)
    let daynumber = myComponents.weekday
    return daynumber
}

输出将如下：

14March（星期一） 15March（星期二） 16March（星期三） 17March（星期四） 18March（星期五） 19March（星期六） 20March（星期日）

答案 13 :(得分：1)

这里已经有很多答案了，但是我认为还有另外一种也许使用更好的Calendar API来做到这一点的方法。

我建议在weekdaySymbols的扩展名中使用Calendar（docs）的Date属性获取星期几：

extension Date {

    /// Returns the day of the week as a `String`, e.g. "Monday"
    var dayOfWeek: String {
        let calendar = Calendar.autoupdatingCurrent
        return calendar.weekdaySymbols[calendar.component(.weekday, from: self) - 1]
    }
}

这需要首先初始化Date，我将使用自定义DateFormatter进行初始化：

extension DateFormatter {

    /// returns a `DateFormatter` with the format "yyyy-MM-dd".
    static var standardDate: DateFormatter {
        let formatter = DateFormatter()
        formatter.dateFormat = "yyyy-MM-dd"
        return formatter
    }
}

然后可以通过以下方式调用它：

DateFormatter.standardDate.date(from: "2018-09-18")!.dayOfWeek

为什么我喜欢这个：

  1. dayOfWeek不必关心时区，因为 使用了用户的日历，此处将显示其他一些解决方案 不正确的日期，因为未考虑时区。
  2. 很有可能您需要在其他日期中使用相同格式的日期 那么为什么不创建可重用的DateFormatter并使用它呢？
  3. weekdaySymbols已为您本地化。
  4. weekDaySymbols可以用其他选项代替，例如shortWeekdaySymbols代表“星期一”，“星期二”等。

请注意：：此示例DateFormatter也不考虑时区或语言环境，您需要根据需要进行设置。如果日期总是准确的，请考虑设置时区TimeZone(secondsFromGMT: 0)。

答案 14 :(得分：0)

如果您想获取全文，请使用以下代码：

func dayOfWeek(date: Date()) -> String? {
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "EEEE"
    return dateFormatter.string(from: date).capitalized 
}


print(Date().dayOfWeek()!) // Monday

或者您想要短文本，请使用以下代码：

func dayOfWeek(date: Date()) -> String? {
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "EEE"
    return dateFormatter.string(from: date).capitalized 
}


print(Date().dayOfWeek()!) // Mon

答案 15 :(得分：0)

SWIFT 5

let MyFormatter = DateFormatter()
MyFormatter.dateFormat = "EE MMM dd"
print(MyFormatter.string(from: Date()))

输出为：Thu Jun 03

可以通过添加 E 或 M 的数量来更改日或月的格式。也可以为年份添加 YY 或 YYYY。

答案 16 :(得分：0)

SWIFT 5-星期几 

    extension Date {

        var dayofTheWeek: String {
             let dayNumber = Calendar.current.component(.weekday, from: self)
             // day number starts from 1 but array count from 0
             return daysOfTheWeek[dayNumber - 1]
        }

        private var daysOfTheWeek: [String] {
             return  ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"]
        }
     }

基于Fattie's answer的日期扩展名

答案 17 :(得分：0)

Swift 3：Xcode 8辅助函数：

func getDayOfWeek(fromDate date: Date) -> String? {
    let cal = Calendar(identifier: .gregorian)
    let dayOfWeek = cal.component(.weekday, from: date)
    switch dayOfWeek {
     case 1:
        return "Sunday"
    case 2:
        return "Monday"
    case 3:
        return "Tuesday"
    case 4:
        return "Wednesday"
    case 5:
        return "Thursday"
    case 6:
        return "Friday"
    case 7:
        return "Saturday"
    default:
        return nil
    }
}

答案 18 :(得分：0)

让Swift4从字符串中获取工作日 

   func getDayOfWeek(today:String)->Int {
        let formatter  = DateFormatter()
        formatter.dateFormat = "yyyy-MM-dd"
        let todayDate = formatter.date(from: today)!
        let myCalendar = NSCalendar(calendarIdentifier: NSCalendar.Identifier.gregorian)!
        let myComponents = myCalendar.components(NSCalendar.Unit.weekday, from: todayDate)
        let weekDay = myComponents.weekday
        return weekDay!
    }

let weekday = getDayOfWeek(today: "2018-10-10")
print(weekday) // 4
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