你如何比较 Swift 中日期的时间？

Question

我有两个日期对象：

1. 2017-01-13 11:40:17 +0000

2. 2016-03-15 10:22:14 +0000

我只需要比较这些值的时间而忽略日期

例如：12:00am 和 12:01am，12:01 更晚（12:01am > 12:00am）== true

Answer 1

我的方法是使用Calendar 使它们成为同一天的Date 对象，然后使用例如timeIntervalSinceReferenceDate 比较它们。

另一种更简洁的方法（但很可能产生更多行代码）是为 Date 创建名为 secondsFromBeginningOfTheDay() -> TimeInterval 的扩展名，然后比较生成的双精度值。

基于第二种方法的示例：

// Creating Date from String
let textDate1 = "2017-01-13T12:21:00-0800"
let textDate2 = "2016-03-06T20:12:05-0900"

let dateFormatter: DateFormatter = {
    let formatter = DateFormatter()
    formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZZZ"
    formatter.timeZone = TimeZone.current
    return formatter
} ()

// Dates used for the comparison
let date1 = dateFormatter.date(from: textDate1)
let date2 = dateFormatter.date(from: textDate2)




// Date extensions
extension Date {
    func secondsFromBeginningOfTheDay() -> TimeInterval {
        let calendar = Calendar.current
        // omitting fractions of seconds for simplicity
        let dateComponents = calendar.dateComponents([.hour, .minute, .second], from: self)

        let dateSeconds = dateComponents.hour! * 3600 + dateComponents.minute! * 60 + dateComponents.second!

        return TimeInterval(dateSeconds)
    }

    // Interval between two times of the day in seconds
    func timeOfDayInterval(toDate date: Date) -> TimeInterval {
        let date1Seconds = self.secondsFromBeginningOfTheDay()
        let date2Seconds = date.secondsFromBeginningOfTheDay()
        return date2Seconds - date1Seconds
    }
}

if let date1 = date1, let date2 = date2 {
    let diff = date1.timeOfDayInterval(toDate: date2)

    // as text
    if diff > 0 {
        print("Time of the day in the second date is greater")
    } else if diff < 0 {
        print("Time of the day in the first date is greater")
    } else {
        print("Times of the day in both dates are equal")
    }


    // show interval as as H M S
    let timeIntervalFormatter = DateComponentsFormatter()
    timeIntervalFormatter.unitsStyle = .abbreviated
    timeIntervalFormatter.allowedUnits = [.hour, .minute, .second]
    print("Difference between times since midnight is", timeIntervalFormatter.string(from: diff) ?? "n/a")

}

// Output: 
// Time of the day in the second date is greater
// Difference between times since midnight is 8h 51m 5s

Answer 2

一天中的时间没有标准类型。一个合理的类型开始只是一个元组：

typealias TimeOfDay = (hour: Int, minute: Int, second: Int)

要创建这些TimeOfDay 值，您需要Calendar。默认情况下，Calendar 使用设备的系统范围的时区。如果您不想这样，请明确设置Calendar 的时区。示例：

var calendar = Calendar.autoupdatingCurrent
calendar.timeZone = TimeZone(abbreviation: "UTC")!

现在您可以使用DateFormatter 将字符串转换为Dates（如有必要），然后使用calendar 从Dates 中提取时间组件：

let strings: [String] = ["2017-01-13 11:40:17 +0000", "2016-03-15 10:22:14 +0000"]
let parser = DateFormatter()
parser.dateFormat = "yyyy-MM-dd HH:mm:ss Z"
let timesOfDay: [TimeOfDay] = strings.map({ (string) -> TimeOfDay in
    let components = calendar.dateComponents([.hour, .minute, .second], from: parser.date(from: string)!)
    return (hour: components.hour!, minute: components.minute!, second: components.second!)
})

Swift.print(timesOfDay)
// Output: [(11, 40, 17), (10, 22, 14)]

最后，您可以比较这些TimeOfDay 值。 Swift 为元素为Comparable 的元组提供了标准的比较运算符，因此TimeOfDay 类型符合条件。你可以这样说：

if timesOfDay[0] < timesOfDay[1] {
    Swift.print("date[0] comes first")
} else if timesOfDay[0] == timesOfDay[1] {
    Swift.print("times are equal")
} else {
    Swift.print("date[1] comes first")
}

Answer 3

这是我最后走的路线，这样很容易在swift中只比较一个日期的时间

新对象时间：

class Time: Comparable, Equatable {
init(_ date: Date) {
    //get the current calender
    let calendar = Calendar.current

    //get just the minute and the hour of the day passed to it
    let dateComponents = calendar.dateComponents([.hour, .minute], from: date)

        //calculate the seconds since the beggining of the day for comparisions
        let dateSeconds = dateComponents.hour! * 3600 + dateComponents.minute! * 60

        //set the varibles
        secondsSinceBeginningOfDay = dateSeconds
        hour = dateComponents.hour!
        minute = dateComponents.minute!
    }

    init(_ hour: Int, _ minute: Int) {
        //calculate the seconds since the beggining of the day for comparisions
        let dateSeconds = hour * 3600 + minute * 60

        //set the varibles
        secondsSinceBeginningOfDay = dateSeconds
        self.hour = hour
        self.minute = minute
    }

    var hour : Int
    var minute: Int

    var date: Date {
        //get the current calender
        let calendar = Calendar.current

        //create a new date components.
        var dateComponents = DateComponents()

        dateComponents.hour = hour
        dateComponents.minute = minute

        return calendar.date(byAdding: dateComponents, to: Date())!
    }

    /// the number or seconds since the beggining of the day, this is used for comparisions
    private let secondsSinceBeginningOfDay: Int

    //comparisions so you can compare times
    static func == (lhs: Time, rhs: Time) -> Bool {
        return lhs.secondsSinceBeginningOfDay == rhs.secondsSinceBeginningOfDay
    }

    static func < (lhs: Time, rhs: Time) -> Bool {
        return lhs.secondsSinceBeginningOfDay < rhs.secondsSinceBeginningOfDay
    }

    static func <= (lhs: Time, rhs: Time) -> Bool {
        return lhs.secondsSinceBeginningOfDay <= rhs.secondsSinceBeginningOfDay
    }


    static func >= (lhs: Time, rhs: Time) -> Bool {
        return lhs.secondsSinceBeginningOfDay >= rhs.secondsSinceBeginningOfDay
    }


    static func > (lhs: Time, rhs: Time) -> Bool {
        return lhs.secondsSinceBeginningOfDay > rhs.secondsSinceBeginningOfDay
    }
}

方便访问的日期扩展： //添加从日期获取时间的功能：

extension Date {
    var time: Time {
        return Time(self)
    }
}

例子：

let firstDate = Date()
let secondDate = firstDate

//Will return true
let timeEqual = firstDate.time == secondDate.time

Answer 4

比公认的答案简单得多：

SWIFT 4

// date1 and date2 are the dates you want to compare

let calendar = Calendar.current

var newDate = Date(TimeIntervalSinceReferenceDate: 0) // Initiates date at 2001-01-01 00:00:00 +0000
var newDate1 = Date(TimeIntervalSinceReferenceDate: 0) // Same as above

// Recieving the components from the dates you want to compare 
let newDateComponents = calendar.dateComponents([.hour, .minute], from: date1)!
let newDate1Components = calendar.dateComponents([.hour, .minute], from: date2)!

// Adding those components
newDate = calendar.date(byAdding: newDateComponents, to: newDate)
newDate1 = calendar.date(byAdding: newDate1Components, to: newDate1)

Answer 5

我在忽略日期的情况下比较一天中的两个时间的解决方案：

let date1 = some time as a date
let date2 = some other time as a date

let time1 = 60*Calendar.current.component(.hour, from: date1!) + Calendar.current.component(.minute, from: date1!)
let time2 =  60*Calendar.current.component(.hour, from: date2!) + Calendar.current.component(.minute, from: date2!)

现在您可以在不考虑日期的情况下比较整数 time1 和 time2。如果您需要更高的精度，可以添加 seconds/60。

Answer 6

如果你使用Swifter Swift，这在 Swift 中非常简单

date1.day = 1
date1.month = 1
date1.year = 2000

date2.day = 1
date2.month = 1
date2.year = 2000

现在您可以在 date1 和 date2 上使用 >,

编辑 - 您可以通过扩展日期类来自己完成此操作，例如 swifter-swift 为 day 组件执行以下操作。

public var day: Int {
        get {
            return Calendar.current.component(.day, from: self)
        }
        set {
            let allowedRange = Calendar.current.range(of: .day, in: .month, for: self)!
            guard allowedRange.contains(newValue) else { return }

            let currentDay = Calendar.current.component(.day, from: self)
            let daysToAdd = newValue - currentDay
            if let date = Calendar.current.date(byAdding: .day, value: daysToAdd, to: self) {
                self = date
            }
        }
    } 

Answer 7

此代码有效，在操场上轻松检查

let s1 = "22:31"
let s2 = "14:31"
let f = DateFormatter()
f.dateFormat = "HH:mm"

f.date(from: s1)! //"Jan 1, 2000 at 10:31 PM"
f.date(from: s2)! //"Jan 1, 2000 at 2:31 PM"
f.date(from: s1)! > f.date(from: s2)!  // true

Answer 8

假设我们有两个字符串格式的日期：

// "2017-01-13 11:40:17 +0000"
// "2016-03-15 10:22:14 +0000"

我们需要将此字符串转换为日期格式，我们创建 DateFormatter() 并设置它要转换的格式 ("yyyy-MM-dd' 'HH:mm:ssZ")

//date formatter converts string to date in our case
let firstDateFormatter = DateFormatter()
firstDateFormatter.dateFormat = "yyyy-MM-dd' 'HH:mm:ssZ"

现在我们可以将日期从字符串转换为日期格式

   //convert string to dates
    if let date1 = firstDateFormatter.date(from: "2017-01-13 09:40:17 +0000"),
        let date2 = firstDateFormatter.date(from: "2016-03-15 10:22:14 +0000") {
    

我们想要的只是比较小时和分钟。所以将日期格式更改为“HH:mm”

//we ve got the dates, now switch dateformat for other job
firstDateFormatter.dateFormat = "HH:mm"

现在从我们的日期中获取字符串值，它只包含“HH:mm”

   // convert date to string ( part of string we want to compare )
        let HHmmDate1 = firstDateFormatter.string(from: date1) //"17:40"
        let HHmmDate2 = firstDateFormatter.string(from: date2) //"18:22"

最后一步是从我们的“HH:mm”值中获取日期，假设我们要求 DateFormatter 给我们一个仅基于时间的日期，在我们的例子中是“17:40”和“18:22”。 DateFormatter 将为日期设置一些值，因此我们会自动为两个日期获取 2000 年 1 月 1 日，但它会获取我们提供的时间。

   //produce "default" dates with desired HH:mm
    //default means same date, but time is different
        let HH1 = firstDateFormatter.date(from: HHmmDate1) //"Jan 1, 2000 at 5:40 PM"
        let HH2 = firstDateFormatter.date(from: HHmmDate2) //"Jan 1, 2000 at 6:22 PM"

现在我们可以轻松比较日期

 //compare
        HH1! > HH2!
}

还有很多选项可以将日期与日历进行比较