Swift - 从数组中获取从今天开始的最后 7 天

Question

如何获取该月的前 7 天如果今天是 18，我知道如何获取，但是如果今天是 11 月 3 日呢？如何在 Int 中获取上个月（10 月）的最后 4 天？

Answer 1

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) 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)

Swift 3（Xcode 8 beta 2）更新：

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)

Answer 2

灵感来自this 答案，

以字符串数组的形式获取前 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"]

Answer 3

您可以使用日历创建扩展程序来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
        }
    }
}

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]

---

与@rintaro 答案相同的策略，尽可能短；）（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）

extension Date {
    func closest(days: Int) -> [Int] {
        return days == 0 ? [] : (1...abs(days)).map { delta -> Int in Calendar.current.component(.day, from: Calendar.current.date(byAdding: .day, value: delta * (days >= 0 ? 1 : -1), to: self)!) }
    }
}

用法：

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]

Answer 4

与@MartinR 答案相同的策略，尽可能短：

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)!)
}

Answer 5

这可能不是最快的代码。但是你明白了:)

import Foundation

let lastSevenDay: [Int] = {
    var days = [Int]()
    let secondsInADay: NSTimeInterval = 24 * 60 * 60
    let now = NSDate()
    let calendar = NSCalendar(calendarIdentifier: NSGregorianCalendar)!
    for i in 1...7 {
        let theDate = now.dateByAddingTimeInterval(-secondsInADay * NSTimeInterval(7 - i))
        let dateComponent = calendar.components(NSCalendarUnit.CalendarUnitDay, fromDate: theDate)
        let dayOfMonth = dateComponent.day
        days.append(dayOfMonth)
    }
    return days
}()

Answer 6

我稍微修改了 rintaro 的答案，以便在 NSDictionaries 的 NSArray 中获取过去的日期，以获取包括过去几天、几个月和几年在内的所有值。你只需要像这样调用这个sn-p

println(getPastDates(2))

获取包含过去日期的完整列表

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

func getPastDates(days: Int) -> NSArray {

    var dates = NSMutableArray()

    let cal = NSCalendar.currentCalendar()

    var today = cal.startOfDayForDate(NSDate())

    for i in 1 ... days {

        let day = cal.component(.DayCalendarUnit, fromDate: today)
        let month = cal.component(.MonthCalendarUnit, fromDate: today)
        let year = cal.component(.YearCalendarUnit, fromDate: today)

        var date = NSMutableDictionary()

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

        dates.addObject(date)

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

    return dates

}

Answer 7

我更新了

Alejandro Luengo 的代码。它适用于 Swift4

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

    }

Answer 8

Swift4

与@MartinR，@rintaro 回答相同的策略，尽可能短：

    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)!)
    }

Answer 9

您想使用NSCalendar 获取最近 7 天。这是一个代码 sn-p，用于在 11 月 3 日演示它：

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)")