swift - 如何使用 DateComponentsFormatter 将日期显示为 "Today"或 "Yesterday"？

Question

我在我的项目中使用 swift 并且我想显示这样的特定日期:5 天前或 5 个月前或 ...
我正在使用 DateComponentsFormatter 并且它运行良好，但问题是我想像“昨天”一样显示 1 天前或像“今天”一样显示 3 秒前。我怎样才能做到这一点？我可以使用 DateComponentsFormatter 来解决这个问题吗？这是我的代码:

func shortDate(_ local: LocaleIdentifier = .fa) -> String {
    
    let now = Date()
    let date = self

    let formatter = DateComponentsFormatter()
    formatter.calendar?.locale = Locale(identifier: local.rawValue)
    formatter.unitsStyle = .full
    formatter.maximumUnitCount = 1
    formatter.allowedUnits = [.year, .month, .day, .hour, .minute, .second]

    guard let timeString = formatter.string(from: date, to: now) else {
         return ""
    }

    return String(format: "Ago".localized, timeString)
}

Answer 1

对于 iOS 13 或更高版本，您可以使用 RelativeDateTimeFormatter

let relativeDateTimeFormatter = RelativeDateTimeFormatter()
relativeDateTimeFormatter.dateTimeStyle = .named
relativeDateTimeFormatter.unitsStyle = .full
let date = Date.init(timeIntervalSinceNow: -60*60*24)
relativeDateTimeFormatter.string(for: date)  // "yesterday"

编辑/更新:
如果您想支持 iOS 11，则需要实现自己的相对日期格式化程序。您可以使用 Calendar 方法 isDateInToday 和 isDateInYesterday 将相对日期格式化程序与日期组件格式化程序结合起来。请注意，无需检查在日期组件格式化程序中设置单个单位的时间间隔，您可以设置日期组件格式化程序的允许单位，只需确保根据要显示的所需优先级设置它们:
//这将避免每次调用 relativeDateFormatted 属性时创建格式化程序

extension Formatter {
    static let dateComponents: DateComponentsFormatter = {
        let dateComponentsFormatter = DateComponentsFormatter()
        dateComponentsFormatter.allowedUnits = [.day, .month, .year]  // check the order of the units it does matter when allowing only 1 unit to be displayed
        dateComponentsFormatter.maximumUnitCount = 1
        dateComponentsFormatter.unitsStyle = .full
        return dateComponentsFormatter
    }()
    static let relativeDate: DateFormatter = {
        let dateFormatter = DateFormatter()
        dateFormatter.doesRelativeDateFormatting = true
        dateFormatter.timeStyle = .none
        dateFormatter.dateStyle = .medium
        return dateFormatter
    }()
}

extension Date {
    var relativeDateFormatted: String {
        Calendar.current.isDateInToday(self) || Calendar.current.isDateInYesterday(self) ?
        Formatter.relativeDate.string(from: self) :
        Formatter.dateComponents.string(from: self, to:  Date()) ?? "" 
    }
}

游乐场测试:

let date1 = DateComponents(calendar: .current, year: 2020, month: 9, day: 4, hour: 5).date!
let date2 = DateComponents(calendar: .current, year: 2020, month: 9, day: 3, hour: 23, minute: 50).date!
let date3 = DateComponents(calendar: .current, year: 2020, month: 8, day: 25, hour: 10).date!
let date4 = DateComponents(calendar: .current, year: 2020, month: 8, day: 3).date!
let date5 = DateComponents(calendar: .current, year: 2019, month: 8, day: 27).date!

date1.relativeDateFormatted  // "Today"
date2.relativeDateFormatted  // "Yesterday"
date3.relativeDateFormatted  // "10 days"
date4.relativeDateFormatted  // "1 month"
date5.relativeDateFormatted  // "1 year"