在 DateFormatter 中使用 NumberFormatter

Question

我正在尝试将我的Date() 格式化为类似于Saturday, June 12th • 5PM - 12PM。我已经能够通过以下DateFormatter() 解决大部分问题：

var date_formatter: DateFormatter {
    let formatter = DateFormatter()
    formatter.dateFormat = "EEEE, MMMM d • HHa - HHa"
    return formatter
}

导致Saturday, June 12 • 5PM - 12PM

我面临的挑战是了解如何添加序数后缀（即 12 -> 12th）。我在NumberFormatter() 上看过一点，但不完全确定如何整合两者。

编辑：最终不得不为5PM - 12PM 逻辑创建两种格式。

这看起来像：

var start_time_formatter: DateFormatter {
        let formatter = DateFormatter()
        formatter.dateFormat = "EEEE, MMMM d • HHa -"
        return formatter
    }

    var end_time_formatter: DateFormatter {
        let formatter = DateFormatter()
        formatter.dateFormat = "HHa"
        return formatter
    }

使用以下内容将其显示在视图中：

Text("\(self.create_event_vm.start_time, formatter: self.start_time_formatter) \(self.create_event_vm.end_time, formatter: self.end_time_formatter)")

我知道这有点古怪，可以使用一些重构，但我希望得到想要的效果，测试，然后重构。

Answer 1

您可以在下面的函数中创建第一个日期后缀

func getDaySuffix(from date: Date) -> String {  
    switch Calendar.current.component(.day, from: date) {
    case 1, 21, 31: return "st"
    case 2, 22: return "nd"
    case 3, 23: return "rd"
    default: return "th"
    }
}

并结合您的代码：

let startDate = Date()
let endDate = Calendar.current.date(byAdding: .hour, value: 5, to: startDate)!

var startTimeFormatter: DateFormatter {
    let formatter = DateFormatter()
    formatter.locale = Locale(identifier: "en_US_POSIX")
    formatter.dateFormat = "EEEE, MMMM d'\(getDaySuffix(from: startDate))' • ha - "
    return formatter
}

var endTimeFormatter: DateFormatter {
    let formatter = DateFormatter()
    formatter.locale = Locale(identifier: "en_US_POSIX")
    formatter.dateFormat = "ha"
    return formatter
}

let startDateResult = startTimeFormatter.string(from: startDate) // "Thursday, June 18th • 2AM - "
let endDateResult = endTimeFormatter.string(from: endDate) // "7AM"
let finalResult = startDateResult + endDateResult // "Thursday, June 18th • 2AM - 7AM"

Answer 2

你走错了路。您需要创建一个 DateInterval 并使用它的 DateIntervalFormatter 将其显示给用户。请注意，下午 12 点已经是另一天了，所以您的日期间隔表示是错误的：

let dateA = DateComponents(calendar: .current, year: 2020, month: 6, day: 12, hour: 17, minute: 0).date!
let dateB = DateComponents(calendar: .current, year: 2020, month: 6, day: 13, hour: 0, minute: 0).date!
let di = DateInterval(start: dateA, end: dateB)
let dif = DateIntervalFormatter()
dif.dateTemplate = "EEEEMMMMdh"
dif.string(from: di)   // "Friday, June 12, 5 PM – Saturday, June 13, 12 AM"

Answer 3

首先是一个有用的扩展Int+Ordinal.swift：

extension Int {

    /// `Int` ordinal suffix
    enum Ordinal: String {

        /// Suffix for numbers ending in `1` except 11
        case st = "st"

        /// Suffix for numbers snding in `2` except 12
        case nd = "nd"

        /// Suffix for numbers ending in `3` except 13
        case rd = "rd"

        /// Suffix otherwise 
        case th = "th"
    }

    /// Get `Ordinal` from `Int` `self`
    var ordinal: Ordinal {
        var mod = self % 100
        if mod == 11 || mod == 12 || mod == 13 {
            return .th
        } else {
            mod = mod % 10
            if mod == 1 {
                return .st
            } else if mod == 2 {
                return .nd
            } else if mod == 3 {
                return .rd
            } else {
                return .th
            }
        }
    }
}

然后使用这个扩展和DateFormatter:

func string(from startDate: Date, to endDate: Date) -> String {
    let formatter = DateFormatter()

    // weekdayMonth
    formatter.dateFormat = "EEEE, MMMM"
    let weekdayMonth = formatter.string(from: startDate)

    // day
    formatter.dateFormat = "d"
    var day = formatter.string(from: startDate)
    if let dayValue = Int(day) {
        day += dayValue.ordinal.rawValue
    }

    // timeFrom
    formatter.dateFormat = "ha"
    let timeFrom = formatter.string(from: startDate)

    // timeTo
    let timeTo = formatter.string(from: endDate)

    return "\(weekdayMonth) \(day) • \(timeFrom) - \(timeTo)"
}

运行它：

let dateString = string(from: Date(), to: Date().addingTimeInterval(3600 * 4))
print(dateString) // "Wednesday, June 17th • 11PM - 3AM"

虽然我猜在这个例子中你不希望它运行到第二天！ :)