如何在Swift中正确计算日期时间差 [英] How to calculate date time difference properly in Swift

问题描述

我想计算两个日期之间的时差，并且时差结果必须类似

I want to calculate time difference between 2 dates, and the time difference result must be something like

7h 12m OR 4 d 5h 27m OR 1M 5d 3h 21m

7h 12m OR 4 d 5h 27m OR 1M 5d 3h 21m

我试图编写这样的函数:

I have tried to write a function like this:

import UIKit

func calculateTimeDifference(from dateTime1: String, to dateTime2: String) -> String {

    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"

    let dateAsString = dateTime1
    let date1 = dateFormatter.date(from: dateAsString)!

    let dateAsString2 = dateTime2
    let date2 = dateFormatter.date(from: dateAsString2)!

    let components : NSCalendar.Unit = [.second, .minute, .hour, .day, .weekOfMonth, .month, .year]
    let difference = (Calendar.current as NSCalendar).components(components, from: date1, to: date2, options: [])

    var dateTimeDifferenceString = ""

    if difference.day != 0 {
        dateTimeDifferenceString = "\(difference.day!)d \(difference.hour!)h \(difference.minute!)m"
    } else if  difference.day == 0 {
        dateTimeDifferenceString = "\(difference.hour!)h \(difference.minute!)m"
    }

    return dateTimeDifferenceString
}

但是当我实现这段代码时

but when I implement this code

let checkinTime = "2018-02-09 07:51:01"
let now = "2018-02-20 14:56:18"

calculateTimeDifference(from: checkinTime, to: now) 

// Result: "4d 7h 5m"

我不知道为什么是4天而不是11天

I don't know why it just 4 days instead of 11 days

但是如果我在同一天实施它，它将给出正确的结果

but if I implement it in the same day, it gives correct result

let checkinTime = "2018-02-09 07:51:01"
let now = "2018-02-09 14:56:18"

calculateTimeDifference(from: checkinTime, to: now)
// "7h 5m"

这里出了什么问题?

推荐答案

在您的第一种情况下，日期之间的差是一个星期，四天后，您会看到，如果您打印计算出的日期部分.

In your first case, the difference between the dates is one week and four days, you'll see that if you print the computed date components.

print(difference)
// year: 0 month: 0 day: 4 hour: 7 minute: 5 second: 17 weekOfMonth: 1 isLeapMonth: false
//                  ^^^^^^                              ^^^^^^^^^^^^^^

所以这就是为什么您得到输出"4d 7h 5m"而不是预期为"11d 7h 5m".要解决此问题，只需删除 .weekOfMonth 从日历单位开始:

So that's why you get the output "4d 7h 5m" instead of the expected "11d 7h 5m". To solve the problem, just remove .weekOfMonth from the calendar units:

let components : NSCalendar.Unit = [.second, .minute, .hour, .day, .month, .year]

此外，您可以直接与 Calendar 一起使用，而无需桥接到 NSCalendar :

In addition, you can work with Calendar directly, without bridging to NSCalendar:

let components: Set<Calendar.Component> = [.second, .minute, .hour, .day, .month, .year]
let difference = Calendar.current.dateComponents(components, from: date1, to: date2)

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