使用NSDate获取星期几

89

我创建了一个方法，该方法应采用“ YYYY-MM-DD”形式的字符串，并吐出一个int，该int表示相对于它所在的星期的日期位置（无论两个月之间是否重叠）。因此，例如，sunday = 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
}

我知道那NSCalendarUnit.WeekdayOrdinalCalendar是错误的，但是我尝试了大多数逻辑组合。并且也搞砸了myComponents.weekdayOrdinal二手mycomponents.day或二手.weekday。

这是我使用方式的选择：

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）。

swift  nsdate  nscalendar 
— Boidkan
source
1
请参阅：ICU格式化日期和时间以格式化字符。
— zaph 2014年
— Suhaib
1
@Suhaib如果看我的标签，它说的是Swift，而不是Objective-C。此外，该代码是在夫特2
— boidkan
在您的dateformatter中尝试以下“ EEEE”
— Alexandros

Answers:

118

您要寻找的是（如果我对问题的理解正确的话）NSCalendarUnit.CalendarUnitWeekday。的对应属性NSDateComponents是weekday。

另请注意，您的日期格式不正确（可以在此处找到完整的规范：http : //unicode.org/reports/tr35/tr35-6.html）。

使用自动类型推断可以稍微简化该函数，在常量足够的情况下，也可以大量使用变量。另外，该函数应返回nil 用于无效输入字符串的可选参数。

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
}

例：

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
    }
}
— 马丁·R
source
是的，那是格式让我感到困惑。当我尝试WeekdayCalendarUnit时，我得到的是2而不是4，非常困惑！感谢您的链接，我将继续阅读。
— boidkan 2014年
1
我知道这不是原始问题的一部分，但是在传入的日期格式不正确或某种程度上无效的情况下，这是返回可选Int的好地方。
— Mike S
1
不应该这样func getDayOfWeek(today:String)->Int?。如果您强行打开可选包装，它仍然会崩溃，不是吗？
— 2014年
1
@HAS：完全正确，谢谢！-在我的测试用例中它没有崩溃，因为可选分配if let ...也可以与隐式解包的可选对象一起使用。
— Martin R
1
谢谢Marting为此，要使您的答案更加美观，您可以对其进行编辑以删除swift 2代码并保留swift 3代码。然后在末尾添加注释：“如果需要快速2的代码，请检查先前的编辑”或类似内容
— Suhaib
154

斯威夫特3＆4

在Swift 3中，检索星期几的编号大大简化了，因为DateComponents它不再是可选的。这是扩展：

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

如果您要查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
— 布兰登
source
1
如果将aDate.dayOfWeek（）放在“用法”下，也许会更清楚。
— boidkan '16
1
请注意，问题是如何从格式为“ YYYY-MM-DD”的字符串中获取工作日。当然，它可以简化您是否已经拥有NSDate。
— 马丁R
4
值得一提的是，如果您在例如中使用它。表格视图，它可能会减慢滚动速度，因为创建DateFormatter的成本很高。如果您要经常使用它，例如，这很好。创建一个实例，并在计算期间将其提供给所有函数调用。
— Vive
绝对。在这种情况下，即使有一个数组处理程序也可以在数据数组上运行该函数，这将很有用。
— brandonscript
1
更简单的只是下面@ david72的答案：Calendar.current.component（.weekday，from：Date（））
— Adam Smaka
37

如果要完整的“星期日”，“星期一”，“星期二”，“星期三”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)
    }
}

我以前的解决方案（仅英语）：

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())
— 马特扬
source
5
EEEEE和EEEEEE会为您提供简短的日期格式，例如Wed，Th，Fr
— Matjan 2016年
1
或使用Calendar的shortWeekdaySymbols属性来避免完全创建DateFormatter。
— mikepj
22

简单答案（第3章）：

Calendar.current.component(.weekday, from: Date())
— 大卫72
source
11

就我而言，我每天都需要三个字母的字符串。我将@Martin R的功能修改如下：

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
    }
}
— 0
source
2
您可以将EEE用作dateFormat
— mrvincenzo '17
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);
    }
— 哈米德
source
2
正在寻找“ EEE”。thanx
— anoo_radha
9 
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)
}
}

用法让weekday = Date（）。weekdayName

— 阿卡什（Akash Shindhe）
source
8

Swift 3日期扩展

extension Date {
    var weekdayOrdinal: Int {
        return Calendar.current.component(.weekday, from: self)
    }
}
— 丰满的
source
我确实在您的答案中添加了一个重点，这是此处的最新答案。如果您不喜欢，显然可以放松一下！:)干杯
— Fattie
这个问题要求一个整数
— quequeful
6

您可以使用此表date_formats 将日期转换为其他格式。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
— qwerty-reloader
source
非常感谢，这就是我在寻找的formatter.dateFormat =“ eeee” //“ eeee”-> Friday
— Mohammed Abunada '18
4

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"]
        }
     }

根据Fattie的答案延长日期

— 帝力
source
3

实际解决方案...

请注意，结果是整数1到7。

（不是零到六。）

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] )
— 胖子
source
3

这里已经有很多答案，但是我认为，使用正确的CalendarAPI可以做到这一点，这是另一种也许更好的方法。

我建议在扩展中使用（docs）的weekdaySymbols属性获取星期几：CalendarDate

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]
    }
}

这需要初始化Date第一个，我将使用自定义进行初始化DateFormatter：

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
    }
}

然后可以使用以下命令调用它：

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

为什么我喜欢这个：

  1. dayOfWeek 不必担心时区，因为使用了用户的日历，此处的其他一些解决方案将显示错误的日期，因为未考虑时区。
  2. 您很有可能需要在其他地方使用相同格式的日期，所以为什么不创建可重复使用的日期 DateFormatter并使用它呢？
  3. weekdaySymbols 为您本地化。
  4. weekDaySymbols可以用其他选项代替，例如shortWeekdaySymbols“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。如果日期总是精确的，请考虑设置时区TimeZone(secondsFromGMT: 0)。

— 里昂
source
1
令人惊讶的是，这是唯一提及的答案weekdaySymbols，谢谢
— Fattie
1

我最终需要从日期开始再添加一些字符串，包括星期几（例如“ 5th”）和一年中的某月（例如8月）。以下是我根据@Martin R函数创建的所有三个函数，并对其进行了修改以返回3个字符字符串：

//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
    }
}
— 0
source
1

SWIFT 2.0代码显示从星期一开始的当前星期。

@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)

}
— Himanshu
source
1

此代码用于查找整个当前星期。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
}

输出将如下所示：

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）

— 阿努拉格·梅塔（Anurag Mehta）
source
1

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
    }
}
— 阿比克斯
source
1
这不是本地化的。
— 亚历山大-恢复莫妮卡
0

对于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
— 塞巴斯蒂安·雷米
source
这与stackoverflow.com/a/25533357/1187415中的第一种方法有何不同？
— Martin R
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