如何从iOS swift中的约会前1小时前获得？

Question

我一直在研究,但我无法找到解决问题的确切方法.我一直试图从一个约会前1小时前得到.我怎样才能在swift中实现这一目标？

Answer 1

对于涉及NSDate的正确计算,考虑到不同日历的所有边缘情况(例如,在节省时间之间切换),您应该使用NSCalendar类:

Swift 3+

let earlyDate = Calendar.current.date(
  byAdding: .hour, 
  value: -1, 
  to: Date())

年长

// Get the date that was 1hr before now
let earlyDate = NSCalendar.currentCalendar().dateByAddingUnit(
       .Hour,
       value: -1, 
       toDate: NSDate(),
       options: [])

Answer 2

使用此方法并粘贴到助手类中.

更新Swift 3和XCode 8.3

  class func timeAgoSinceDate(_ date:Date,currentDate:Date, numericDates:Bool) -> String {
    let calendar = Calendar.current
    let now = currentDate
    let earliest = (now as NSDate).earlierDate(date)
    let latest = (earliest == now) ? date : now
    let components:DateComponents = (calendar as NSCalendar).components([NSCalendar.Unit.minute , NSCalendar.Unit.hour , NSCalendar.Unit.day , NSCalendar.Unit.weekOfYear , NSCalendar.Unit.month , NSCalendar.Unit.year , NSCalendar.Unit.second], from: earliest, to: latest, options: NSCalendar.Options())

    if (components.year! >= 2) {
        return "\(components.year!) years ago"
    } else if (components.year! >= 1){
        if (numericDates){
            return "1 year ago"
        } else {
            return "Last year"
        }
    } else if (components.month! >= 2) {
        return "\(components.month!) months ago"
    } else if (components.month! >= 1){
        if (numericDates){
            return "1 month ago"
        } else {
            return "Last month"
        }
    } else if (components.weekOfYear! >= 2) {
        return "\(components.weekOfYear!) weeks ago"
    } else if (components.weekOfYear! >= 1){
        if (numericDates){
            return "1 week ago"
        } else {
            return "Last week"
        }
    } else if (components.day! >= 2) {
        return "\(components.day!) days ago"
    } else if (components.day! >= 1){
        if (numericDates){
            return "1 day ago"
        } else {
            return "Yesterday"
        }
    } else if (components.hour! >= 2) {
        return "\(components.hour!) hours ago"
    } else if (components.hour! >= 1){
        if (numericDates){
            return "1 hour ago"
        } else {
            return "An hour ago"
        }
    } else if (components.minute! >= 2) {
        return "\(components.minute!) minutes ago"
    } else if (components.minute! >= 1){
        if (numericDates){
            return "1 minute ago"
        } else {
            return "A minute ago"
        }
    } else if (components.second! >= 3) {
        return "\(components.second!) seconds ago"
    } else {
        return "Just now"
    }

}

使用此方法:

var timeAgo:String=AppHelper.timeAgoSinceDate(date, numericDates: true)
Print("\(timeAgo)")   // Ex- 1 hour ago

Answer 3

请阅读NSDate课程参考.

let oneHourAgo = NSDate.dateWithTimeIntervalSinceNow(-3600)

应该这样做.

或者,对于任何NSDate对象:

let oneHourBack = myDate.dateByAddingTimeInterval(-3600)

Answer 4

根据您的需要,您可以从一个Date实例中选择以下3个Swift 3方法中的一个来获取一个小时.

1. date(byAdding:value:to:wrappingComponents:)

Calendar有一个叫做的方法date(byAdding:value:to:wrappingComponents:).date(byAdding:value:to:wrappingComponents:)有以下声明:

func date(byAdding component: Calendar.Component, value: Int, to date: Date, wrappingComponents: Bool = default) -> Date?

返回Date表示通过将特定组件的数量添加到给定日期而计算的日期的新值.

下面的Playground代码显示了如何使用它:

import Foundation

let now = Date()
let oneHourAgo = Calendar.current.date(byAdding: .hour, value: -1, to: now)

print(now) // 2016-12-19 21:52:04 +0000
print(String(describing: oneHourAgo)) // Optional(2016-12-19 20:52:04 +0000)

2. date(byAdding:to:wrappingComponents:)

Calendar有一个叫做的方法date(byAdding:to:wrappingComponents:).date(byAdding:value:to:wrappingComponents:)有以下声明:

func date(byAdding components: DateComponents, to date: Date, wrappingComponents: Bool = default) -> Date?

返回Date表示通过向给定日期添加组件计算的日期的新值.

下面的Playground代码显示了如何使用它:

import Foundation

let now = Date()

var components = DateComponents()
components.hour = -1
let oneHourAgo = Calendar.current.date(byAdding: components, to: now)

print(now) // 2016-12-19 21:52:04 +0000
print(String(describing: oneHourAgo)) // Optional(2016-12-19 20:52:04 +0000)

替代方案:

import Foundation

// Get the date that was 1hr before now
let now = Date()

let components = DateComponents(hour: -1)
let oneHourAgo = Calendar.current.date(byAdding: components, to: now)

print(now) // 2016-12-19 21:52:04 +0000
print(String(describing: oneHourAgo)) // Optional(2016-12-19 20:52:04 +0000)

3. addingTimeInterval(_:)(谨慎使用)

Date有一个叫做的方法addingTimeInterval(_:).addingTimeInterval(_:)有以下声明:

func addingTimeInterval(_ timeInterval: TimeInterval) -> Date

Date通过添加一个TimeInterval来返回一个新的Date.

请注意,此方法附带警告:

这仅调整绝对值.如果您希望添加日历,日期,月份等日历概念,则必须使用Calendar.这将考虑到诸如夏令时,具有不同天数的月份等复杂性.

下面的Playground代码显示了如何使用它:

import Foundation

let now = Date()
let oneHourAgo = now.addingTimeInterval(-3600)

print(now) // 2016-12-19 21:52:04 +0000
print(oneHourAgo) // 2016-12-19 20:52:04 +0000

Answer 5

如果您正在使用NSDate，则可以执行以下操作：

let date = NSDate()
date.dateByAddingTimeInterval(-3600)

它将date对象更改为“ 1小时前”。

Answer 6

斯威夫特3：

let now = Date()
let tempCalendar = Calendar.current
let alteredDate = tempCalendar.date(byAdding: .hour, value: -1, to: now)