Ios Swift-从今天开始在阵列中获得最后7天

如何获得一个月的前7天如果今天是18天我知道如何获得，但是如果今天是11月3日呢？如何获取上个月（10月）最后4天的整数？

这可能不是最快的代码。但你明白了：）

---

使用

NSCalendar

和

NSDateComponents

：

let cal = NSCalendar.currentCalendar()
// start with today
var date = cal.startOfDayForDate(NSDate())

var days = [Int]()

for i in 1 ... 7 {
    // get day component:
    let day = cal.component(.DayCalendarUnit, fromDate: date)
    days.append(day)

    // move back in time by one day:
    date = cal.dateByAddingUnit(.DayCalendarUnit, value: -1, toDate: date, options: nil)!
}

println(days)

Swift 2.2（Xcode 7.3.1）的更新：

let cal = NSCalendar.currentCalendar()
var date = cal.startOfDayForDate(NSDate())
var days = [Int]()
for i in 1 ... 7 {
    let day = cal.component(.Day, fromDate: date)
    days.append(day)
    date = cal.dateByAddingUnit(.Day, value: -1, toDate: date, options: [])!
}
print(days)

let cal = Calendar.current
var date = cal.startOfDay(for: Date())
var days = [Int]()
for i in 1 ... 7 {
    let day = cal.component(.day, from: date)
    days.append(day)
    date = cal.date(byAdding: .day, value: -1, to: date)!
}
print(days)

更新Swift 3（Xcode 8 beta 2）：

let cal = NSCalendar.currentCalendar()
var date = cal.startOfDayForDate(NSDate())
var days = [Int]()
for i in 1 ... 7 {
    let day = cal.component(.Day, fromDate: date)
    days.append(day)
    date = cal.dateByAddingUnit(.Day, value: -1, toDate: date, options: [])!
}
print(days)

let cal = Calendar.current
var date = cal.startOfDay(for: Date())
var days = [Int]()
for i in 1 ... 7 {
    let day = cal.component(.day, from: date)
    days.append(day)
    date = cal.date(byAdding: .day, value: -1, to: date)!
}
print(days)

---

与@MartinR answer相同的策略，尽可能简短：

let cal = NSCalendar.currentCalendar()
let date = NSDate()

var result = map(-6...0) { delta -> Int in
    cal.component(.DayCalendarUnit, fromDate: cal.dateByAddingUnit(.DayCalendarUnit, value: delta, toDate: date, options: nil)!)
}

    let calendar = Calendar.current
    let date = Date()

    let result: [Int] = (-6...0).map { delta -> Int in
        calendar.component(.day, from: calendar.date(byAdding: .day, value: delta, to: date)!)
    }

---

您想使用

NSCalendar

获取最后7天的时间。下面是一段代码片段，用于在11月3日的活动中演示它：

let dateFormatter = NSDateFormatter()
dateFormatter.dateStyle = .ShortStyle
dateFormatter.timeStyle = .NoStyle
dateFormatter.locale = NSLocale(localeIdentifier: "en_GB")
let date = dateFormatter.dateFromString("03/11/14")!
println("date = \(dateFormatter.stringFromDate(date))")

let calendar = NSCalendar(calendarIdentifier: NSGregorianCalendar)!
var previous7days: Array<Int> = []
for i in 0...6 {
    let prevDate = calendar.dateByAddingUnit(.CalendarUnitDay, value: -i, toDate: date, options:  nil)
    previous7days.insert(calendar.component(.CalendarUnitDay, fromDate: prevDate!), atIndex: 0)
}
println("last 7 days: \(previous7days)")

let dateFormatter=NSDateFormatter（）
dateFormatter.dateStyle=.ShortStyle
dateFormatter.timeStyle=.NoStyle
dateFormatter.locale=NSLocale（localeIdentifier:“en_GB”）
让date=dateFormatter.dateFromString（“03/11/14”）！
println（“日期=\（dateFormatter.stringFromDate（日期）））
让calendar=NSCalendar（calendarIdentifier:NSGregorianCalendar）！
var-previous7days:Array=[]
因为我在0…6{
让prevDate=calendar.dateByAddingUnit（.CalendarUnitDay，值：-i，toDate:date，选项：nil）
previous7days.insert（calendar.component（.CalendarUnitDay，fromDate:PreviousDate！），索引：0）
}
println（“最近7天：\（以前7天）”）

我稍微修改了rintaro答案，以获取NSArray NSDictionary中的过去日期，从而获取所有值，包括过去的天数、月份和年份。您只需要像这样调用此代码段

println(getPastDates(2))

得到一份完整的过去日期的清单

( { 日=30； 月=11； 年份=2014年； }, { 日=29； 月=11； 年份=2014年； } )

---

您可以使用日历创建扩展，以帮助您进行日历计算：

Swift 3或更高版本

extension Date {
    var day: Int {
        return Calendar.current.component(.day, from: self)
    }
    func adding(days: Int) -> Date {
        return Calendar.current.date(byAdding: .day, value: days, to: self)!
    }
    var last7days: [Int] {
        return (1...7).map { 
            adding(days: -$0).day
        }
    }
    func near(days: Int) -> [Int] {
        return days == 0 ? [day] : (1...abs(days)).map {
            adding(days: $0 * (days < 0 ? -1 : 1) ).day
        }
    }
}

---

与@rintaro answer相同的策略，尽可能简短；）（增加了对负值的支持，并将其作为日期扩展，以便能够使用任何日期作为输入）

用法：

let last7Days  = Date().last7days   // [29, 28, 27, 26, 25, 24, 23]
let last7Days2 = Date().near(days: -7) // [29, 28, 27, 26, 25, 24, 23]
let next7Days  = Date().near(days: 7) // [27, 28, 29, 30, 31, 1, 2]

let next7Days2 = Date().closest(days: 7) // [27, 28, 29, 30, 31, 1, 2]
let last7Days3 = Date().closest(days: -7) // [25, 24, 23, 22, 21, 20, 19]
let next2Days = Date().closest(days: 2) // [27, 28]
let last2Days = Date().closest(days: -2) // [25, 24]

我更新

亚历杭德罗·卢恩戈的密码。它工作得很快

func getPastDates(days: Int) -> NSMutableArray {

        let dates = NSMutableArray()
        let calendar = Calendar.current

        var today = calendar.startOfDay(for: Date())

        for _ in 1 ... days {

            let day = calendar.component(.day, from: today)
            let month = calendar.component(.month, from: today)
            let year = calendar.component(.year, from: today)

            let date = NSMutableDictionary()

            date.setValue(day, forKey: "day")
            date.setValue(month, forKey: "month")
            date.setValue(year, forKey: "year")

            dates.add(date)
            today = calendar.date(byAdding: .day, value: -1, to: today)!
        }

        return dates

    }

受到答案的启发

以字符串数组的形式获取以前N天的列表

extension Date {
    static func getDates(forLastNDays nDays: Int) -> [String] {
        let cal = NSCalendar.current
        // start with today
        var date = cal.startOfDay(for: Date())

        var arrDates = [String]()

        for _ in 1 ... nDays {
            // move back in time by one day:
            date = cal.date(byAdding: Calendar.Component.day, value: -1, to: date)!

            let dateFormatter = DateFormatter()
            dateFormatter.dateFormat = "yyyy-MM-dd"
            let dateString = dateFormatter.string(from: date)
            arrDates.append(dateString)
        }
        print(arrDates)
        return arrDates
    }
}

用法：

let last7Days = Date.getDates(forLastNDays: 7)
debugPrint(last7Days)

//Today(2017-11-19) it prints: ["2017-11-18", "2017-11-17", "2017-11-16", "2017-11-15", "2017-11-14", "2017-11-13", "2017-11-12"]

---

Swift4

与@MartinR相同的策略，@rintaro-answer，尽可能简短：

let cal = NSCalendar.currentCalendar()
let date = NSDate()

var result = map(-6...0) { delta -> Int in
    cal.component(.DayCalendarUnit, fromDate: cal.dateByAddingUnit(.DayCalendarUnit, value: delta, toDate: date, options: nil)!)
}

    let calendar = Calendar.current
    let date = Date()

    let result: [Int] = (-6...0).map { delta -> Int in
        calendar.component(.day, from: calendar.date(byAdding: .day, value: delta, to: date)!)
    }

---

你所说的

Int

是什么意思？Unix时间戳或其他什么？[27,28,29,30,1,2,3]或[28,29,30,31,1,2,3]这取决于月份。每天没有86400秒（想想夏时制和夏时制之间的转换）。使用60*60*24作为一天的持续时间是错误的。是的，这就是为什么你的答案更好；）闰秒是否需要

.startOfDayForDate（）

？@rintaro：在处理日期时，我更喜欢定义明确的时间组件。但这并不是真的需要。Unix时间中不考虑闰秒，因此它不起任何作用。@如果您回答我的问题，MartinR将不胜感激@MartinR:What's way to reach the days like

[Dec 26，Dec 27]

this format？@iPeter:使用DateFormatter将日期转换为字符串。您可以在下面的其他答案中找到示例，例如，并非每天都有86400秒（想想夏时制和夏时制之间的转换）。用60*60*24作为一天的持续时间是错误的。谢谢你指出这一点。我们这里没有DST，所以我没想过。我对你的解决方案投了赞成票，因为它正确且更简洁：）很好。我喜欢你使用地图的方式我很感激你D