使用 NSDate 获取星期几 [英] Get day of week using NSDate

问题描述

我创建了一个方法，该方法应该以YYYY-MM-DD"形式接收一个字符串，并吐出一个 int 来表示与其所在周相关的日期位置(无论它是否在月份之间重叠).所以例如 sunday=1 monday=2 等等.

I created a method that is supposed to take in a string in "YYYY-MM-DD" form and spit out an int that represents the dates position in relation to the week it is in (regardless if it overlaps between months). So e.g sunday=1 monday=2 and so on.

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，但我尝试过我认为大多数逻辑组合.并且还使用了 myComponents.weekdayOrdinal，例如使用了 mycomponents.day 或 .weekday.

I know that NSCalendarUnit.WeekdayOrdinalCalendar is wrong but I have tried I think most logical combinations. And have also messed around with myComponents.weekdayOrdinal e.g used mycomponents.day or .weekday.

以下是我的选择:

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).

It is not clear to me since there is no DayOfWeekUnit option (or something similar).

推荐答案

您正在寻找的(如果我理解正确的话)是 NSCalendarUnit.CalendarUnitWeekday.NSDateComponents 对应的属性是weekday.

What you are looking for (if I understand the question correctly) is NSCalendarUnit.CalendarUnitWeekday. The corresponding property of NSDateComponents is weekday.

还要注意您的日期格式是错误的(完整规范可以在这里找到:http://unicode.org/reports/tr35/tr35-6.html).

Note also that your date format is wrong (the full specification can be found here: http://unicode.org/reports/tr35/tr35-6.html).

该函数可以稍微简化，使用自动类型推断，您也可以在常量足够的地方使用很多变量.此外，该函数应该返回一个可选的 nil对于无效的输入字符串.

The function can be simplified slightly, using automatic type inference, also you use variables a lot where constants are sufficient. In addition, the function should return an optional which is nil for an invalid input string.

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:

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
    }
}

这篇关于使用 NSDate 获取星期几的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！