可跨越的日期

Question

我正在寻找很酷的方法来跨越 Date 范围以不同的增量（秒又名 TimeInterval 或 DateComponents 又名 .hour、.minute）

import Foundation

extension Date: Strideable {
    // typealias Stride = SignedInteger // doesn't work (probably because declared in extension
    public func advanced(by n: Int) -> Date {
        self.addingTimeInterval(TimeInterval(n))
    }

    public func distance(to other: Date) -> Int {
        return Int(self.distance(to: other))
    }
}
let now = Date()

let dayAfterNow = Date().addingTimeInterval(86400)
let dateRange = now ... dayAfterNow
let dateArr : [Date] = Array(stride(from: now, to: dayAfterNow, by: 60)) // Solves my task but  not exactly how I wanted.
let formatter: DateFormatter = {
    let df = DateFormatter()
    df.timeStyle = .short
    return df }()
print (dateArr.prefix(7).map { formatter.string(from: $0) })

/// This hoever doesn't work
// There must be a way to make it work but couldn't figure it out for now
let errDateArr: [Date] = Array(dateRange)
// Error: Initializer 'init(_:)' requires that 'Date.Stride' (aka 'Double') conform to 'SignedInteger'

问题的第二部分是我也想要类似的东西：

var components = DateComponents()
components.hour = 8
components.minute = 0
let date = Calendar.current.date(from: components)
let dateByComponentArr : [Date] = Array(stride(from: now, to: dayAfterNow, by: components))

Answer 1

正如@Alexander 已经提到的，您不应该尝试将 Date 与 Strideable 保持一致，但您可以实现自己的方法来生成接下来的 n 天、小时或分钟：

extension Date {
    func year(using calendar: Calendar = .current) -> Int { calendar.component(.year, from: self) }
    func month(using calendar: Calendar = .current) -> Int { calendar.component(.month, from: self) }
    func day(using calendar: Calendar = .current) -> Int { calendar.component(.day, from: self) }
    func hour(using calendar: Calendar = .current) -> Int { calendar.component(.hour, from: self) }
    func minute(using calendar: Calendar = .current) -> Int { calendar.component(.minute, from: self) }
    func nextDays(n: Int, nth: Int = 1, using calendar: Calendar = .current) -> [Date] {
        let year  = self.year(using: calendar)
        let month = self.month(using: calendar)
        let day   = self.day(using: calendar)
        var days: [Date] = []
        for x in 0..<n where x.isMultiple(of: nth) {
            days.append(DateComponents(calendar: calendar, year: year, month: month, day: day + x, hour: 12).date!)

        }
        return days
    }
    func nextHours(n: Int, nth: Int = 1, using calendar: Calendar = .current) -> [Date] {
        let year  = self.year(using: calendar)
        let month = self.month(using: calendar)
        let day   = self.day(using: calendar)
        let hour   = self.hour(using: calendar)
        var hours: [Date] = []
        for x in 0..<n where x.isMultiple(of: nth) {
            hours.append(DateComponents(calendar: calendar, year: year, month: month, day: day, hour: hour + x).date!)

        }
        return hours
    }
    func nextMinutes(n: Int, nth: Int = 1, using calendar: Calendar = .current) -> [Date] {
        let year  = self.year(using: calendar)
        let month = self.month(using: calendar)
        let day   = self.day(using: calendar)
        let hour   = self.hour(using: calendar)
        let minute   = self.minute(using: calendar)
        var minutes: [Date] = []
        for x in 0..<n where x.isMultiple(of: nth) {
            minutes.append(DateComponents(calendar: calendar, year: year, month: month, day: day, hour: hour, minute: minute + x).date!)

        }
        return minutes
    }
}

---

extension Date {
    static let formatter: DateFormatter = {
        let formatter = DateFormatter()
        formatter.dateStyle = .short
        formatter.timeStyle = .short
        return formatter
    }()
}

---

游乐场测试：

let days = Date().nextDays(n: 10)
for day in days {
    print(Date.formatter.string(from: day))
}

let hours = Date().nextHours(n: 10)
for hour in hours {
    print(Date.formatter.string(from: hour))
}

let minutes = Date().nextMinutes(n: 10)
for minute in minutes {
    print(Date.formatter.string(from: minute))
}

Answer 2

distance(to:) 的实现存在冲突，已在 Date:Date.distance(to:) 上声明。您定义的实现具有相同的名称，但类型不同。这个其他重载可以工作，但不幸的是，Date 已经声明了一个名为Stride 的类型别名，它设置为TimeInterval（只是Double 的别名）。

我认为遵循Date 到Strideable 是个坏主意。以Double 为例，它有意 不符合Strideable：没有明确的普遍最佳步幅定义。它应该上升0.1 吗？ 0.01? 3.14?这并不明显。 stride(from:to:by:) 存在 正是出于这个原因，以便您明确指出自己的步伐。

let errDateArr: [Date] = Array(now ... dayAfterNow) 肯定会高分"WTFs/m" points

Answer 3

对于问题的第二部分，我创建了一个简单的序列，其中考虑了夏令时设置和其他内容。在某些特定情况下可能会有所帮助。

let dayAfterNow = Date().addingTimeInterval(86400)
var components = DateComponents()
components.hour = 8
components.minute = 0

func dateIterator(start: Date = Date(), by components: DateComponents, wrappingComponents: Bool = false) -> AnyIterator<Date> {
    var state = start
    return AnyIterator {
        
        let nextDate = Calendar.current.date(byAdding: components, to: state, wrappingComponents: wrappingComponents)
        state = nextDate ?? state
        return state
    }    
}


let dateCompSequence = AnySequence(dateIterator(by: components))
let dateArray = Array(dateCompSequence.prefix(10))
dateArray.map{print($0.description)}
print("starting for loop...")

for d in dateCompSequence.prefix(10) {
    print(d.description)
}

值得注意的是，Calendar.current.enumerateDates() 可能总是会帮助完成类似的任务。但有时最好有一个顺序。在早期版本的 Swift 中，NSCalendar 提供了一个可跨步的 DateRange 类型（正是我想要的），但现在标准库中没有类似的东西。