swift - 如何快速创建当前星期日期的数组

Question

我正在开展一个项目，我需要本周的日期。我目前正在使用此函数来获取当前日期。

func getDay() -> String {
    let date = Date()
    let formatter = DateFormatter()
    formatter.dateFormat = "dd.MM.yyyy"
    let result = formatter.string(from: date)
    return result
}

它可以很好地为我提供一个约会，但我不知道如何获得本周的所有 7 个日期。如果有人可以提供帮助，我们将不胜感激。

Answer 1

您可以获得今天的yearForWeekOfYear 和weekOfYear 日历组件并从中构造一个新日期。它将为您提供一周的第一天。如果您希望一周从星期一开始，您需要使用 iso8601 日历，如果您希望一周从星期日开始，您可以使用公历。为了避免一些极端情况，您应该使用中午时间进行所有日历计算。并非所有日期都从午夜开始。

let dateComponents = Calendar(identifier: .gregorian).dateComponents([.yearForWeekOfYear, .weekOfYear], from: Date())
let startOfWeek = Calendar(identifier: .gregorian).date(from: dateComponents)!
let startOfWeekNoon = Calendar(identifier: .gregorian).date(bySettingHour: 12, minute: 0, second: 0, of: startOfWeek)!
let weekDays = (0...6).map { Calendar(identifier: .gregorian).date(byAdding: .day, value: $0, to: startOfWeekNoon)! }
weekDays  // ["Jun 7, 2020 at 12:00 PM", "Jun 8, 2020 at 12:00 PM", "Jun 9, 2020 at 12:00 PM", "Jun 10, 2020 at 12:00 PM", "Jun 11, 2020 at 12:00 PM", "Jun 12, 2020 at 12:00 PM", "Jun 13, 2020 at 12:00 PM"]

---

在此基础上，您可以扩展 Date 并创建一些助手:

extension Calendar {
    static let iso8601 = Calendar(identifier: .iso8601)
    static let gregorian = Calendar(identifier: .gregorian)
}

---

extension Date {
    func byAdding(component: Calendar.Component, value: Int, wrappingComponents: Bool = false, using calendar: Calendar = .current) -> Date? {
        calendar.date(byAdding: component, value: value, to: self, wrappingComponents: wrappingComponents)
    }
    func dateComponents(_ components: Set<Calendar.Component>, using calendar: Calendar = .current) -> DateComponents {
        calendar.dateComponents(components, from: self)
    }
    func startOfWeek(using calendar: Calendar = .current) -> Date {
        calendar.date(from: dateComponents([.yearForWeekOfYear, .weekOfYear], using: calendar))!
    }
    var noon: Date {
        Calendar.current.date(bySettingHour: 12, minute: 0, second: 0, of: self)!
    }
    func daysOfWeek(using calendar: Calendar = .current) -> [Date] {
        let startOfWeek = self.startOfWeek(using: calendar).noon
        return (0...6).map { startOfWeek.byAdding(component: .day, value: $0, using: calendar)! }
    }
}

---

用法:

// this will give you all days of the current week starting monday
Date().daysOfWeek(using: .iso8601)  // ["Jun 8, 2020 at 12:00 PM", "Jun 9, 2020 at 12:00 PM", "Jun 10, 2020 at 12:00 PM", "Jun 11, 2020 at 12:00 PM", "Jun 12, 2020 at 12:00 PM", "Jun 13, 2020 at 12:00 PM", "Jun 14, 2020 at 12:00 PM"]
// this will give you all days of the current week starting sunday
Date().daysOfWeek(using: .gregorian) // ["Jun 7, 2020 at 12:00 PM", "Jun 8, 2020 at 12:00 PM", "Jun 9, 2020 at 12:00 PM", "Jun 10, 2020 at 12:00 PM", "Jun 11, 2020 at 12:00 PM", "Jun 12, 2020 at 12:00 PM", "Jun 13, 2020 at 12:00 PM"]

---

要将日期转换为固定日期格式，您可以创建一个扩展格式化程序和日期的自定义日期格式化程序:

extension Formatter {
    static let ddMMyyyy: DateFormatter = {
        let dateFormatter = DateFormatter()
        dateFormatter.calendar = Calendar(identifier: .iso8601)
        dateFormatter.locale = .init(identifier: "en_US_POSIX")
        dateFormatter.dateFormat = "dd.MM.yyyy"
        return dateFormatter
    }()
}

---

extension Date {
    var ddMMyyyy: String { Formatter.ddMMyyyy.string(from: self) }
}

---

现在您可以使用 KeyPath 简单地映射日期:

Date().daysOfWeek(using: .gregorian).map(\.ddMMyyyy) // ["07.06.2020", "08.06.2020", "09.06.2020", "10.06.2020", "11.06.2020", "12.06.2020", "13.06.2020"]