Swift - 检查时间戳是昨天，今天，明天还是X天前 [英] Swift - check if a timestamp is yesterday, today, tomorrow, or X days ago

问题描述

我正在尝试弄清楚如何确定今天是否发生给定时间戳，或+1 / -1天。基本上，我想做这样的事情（伪代码）

I'm trying to work out how to decide if a given timestamp occurs today, or +1 / -1 days. Essentially, I'd like to do something like this (Pseudocode)

IF days_from_today(timestamp) == -1 RETURN 'Yesterday'
ELSE IF days_from_today(timestamp) == 0 RETURN 'Today'
ELSE IF days_from_today(timestamp) == 1 RETURN 'Tomorrow'
ELSE IF days_from_today(timestamp) < 1 RETURN days_from_today(timestamp) + ' days ago'
ELSE RETURN 'In ' + days_from_today(timestamp) + ' ago'

但至关重要的是，它需要在Swift中，我正在努力使用NSDate / NSCalendar对象。我开始计算这样的时差：

Crucially though, it needs to be in Swift and I'm struggling with the NSDate / NSCalendar objects. I started with working out the time difference like this:

let calendar = NSCalendar.currentCalendar()
let date = NSDate(timeIntervalSince1970: Double(timestamp))
let timeDifference = calendar.components([.Second,.Minute,.Day,.Hour],
    fromDate: date, toDate: NSDate(), options: NSCalendarOptions())

然而，以这种方式比较并不容易，因为 .Day 根据一天中的时间和时间戳而有所不同。在PHP中，我只是使用mktime创建一个基于当天开始的新日期（即 mktime（0,0,0）），但我是不确定在Swift中最简单的方法。

However comparing in this way isn't easy, because the .Day is different depending on the time of day and the timestamp. In PHP I'd just use mktime to create a new date, based on the start of the day (i.e. mktime(0,0,0)), but I'm not sure of the easiest way to do that in Swift.

有没有人对如何处理这个问题有个好主意？也许NSDate的扩展或类似的东西最好？

Does anybody have a good idea on how to approach this? Perhaps an extension to NSDate or something similar would be best?

推荐答案

NSCalendar 具有所有三种情况的方法

NSCalendar has methods for all three cases

func isDateInYesterday(_ date: NSDate) -> Bool
func isDateInToday(_ date: NSDate) -> Bool
func isDateInTomorrow(_ date: NSDate) -> Bool

要计算早于昨天的天数，请使用

To calculate the days earlier than yesterday use

func components(_ unitFlags: NSCalendarUnit,
      fromDate startingDate: NSDate,
          toDate resultDate: NSDate,
               options opts: NSCalendarOptions) -> NSDateComponents

将 .Day 传递给 unitFlags 并从结果中获取天属性。

pass .Day to unitFlags and get the day property from the result.

编辑：

这是一个函数，它通过剥离时间部分来考虑在中的早期和晚期日期。

This is a function which considers also is in for earlier and later dates by stripping the time part.

func dayDifferenceFromDate(timestamp : Int) -> String
{
  let calendar = NSCalendar.currentCalendar()
  let date = NSDate(timeIntervalSince1970: Double(timestamp))
  if calendar.isDateInYesterday(date) { return "Yesterday" }
  else if calendar.isDateInToday(date) { return "Today" }
  else if calendar.isDateInTomorrow(date) { return "Tomorrow" }
  else {
    let startOfNow = calendar.startOfDayForDate(NSDate())
    let startOfTimeStamp = calendar.startOfDayForDate(date)
    let components = calendar.components(.Day, fromDate: startOfNow, toDate: startOfTimeStamp, options: [])
    let day = components.day
    if day < 1 { return "\(abs(day)) days ago" }
    else { return "In \(day) days" }
  }
}

Swift 3 +的更新：

func dayDifference(from interval : TimeInterval) -> String
{
    let calendar = NSCalendar.current
    let date = Date(timeIntervalSince1970: interval)
    if calendar.isDateInYesterday(date) { return "Yesterday" }
    else if calendar.isDateInToday(date) { return "Today" }
    else if calendar.isDateInTomorrow(date) { return "Tomorrow" }
    else {
        let startOfNow = calendar.startOfDay(for: Date())
        let startOfTimeStamp = calendar.startOfDay(for: date)
        let components = calendar.dateComponents([.day], from: startOfNow, to: startOfTimeStamp)
        let day = components.day!
        if day < 1 { return "\(abs(day)) days ago" }
        else { return "In \(day) days" }
    }
}

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