从日期数组中获取日期数组

Question

我有一个 Date 对象数组，如下例所示：

let dates = [date1, date2, date3, date4, date5]

如何为具有相同 day of month、month 和 year.

的日期创建子数组

示例：

date1 = 20/04/2020
date2 = 19/04/2020
date3 = 19/04/2020
date4 = 18/04/2020
date5 = 18/04/2020
...

有了这个，我想要以下内容：

let group1 = [date1]
let group2 = [date2, date3] 
let group3 = [date4, date5]
let group4 = //...

我尝试了 DateComponents 和 .map、.filter 等功能，但不知何故我无法做到这一点。

我能得到提示吗？

谢谢。

Answer 1

只需创建跟踪年月日的结构。

struct DateCluster {
    let day: Int
    let month: Int
    let year: Int

    var dates: [Date] = []

    init(date: Date) {
        let cal = Calendar.current
        day = cal.component(.day, from: date)
        month = cal.component(.month, from: date)
        year = cal.component(.year, from: date)

        dates.append(date)
    }

    func doesDateBelong(_ date: Date) -> Bool {
        let cal = Calendar.current
        return cal.component(.day, from: date) == day
            && cal.component(.month, from: date) == month
            && cal.component(.year, from: date) == year
    }
}

这是用法：

func makeDate(year: Int, month: Int, day: Int) -> Date? {
    let cal = Calendar.current
    let components = DateComponents(year: year, month: month, day: day)
    return cal.date(from: components)
}

var clusters: [DateCluster] = []


var dates = [
    makeDate(year: 2020, month: 4, day: 20),
    makeDate(year: 2020, month: 4, day: 19),
    makeDate(year: 2020, month: 4, day: 19),
    makeDate(year: 2020, month: 4, day: 18),
    makeDate(year: 2020, month: 4, day: 18),
].compactMap { [=11=] }


for date in dates {
    if let index = clusters.firstIndex(where: { [=11=].doesDateBelong(date) }) {
        clusters[index].dates.append(date)
    } else {
        clusters.append(.init(date: date))
    }
}

下面的结果将是所有按年月日分组的日期数组。

let groupedDates = clusters.map { [=12=].dates }

Answer 2

该代码从每个日期中提取年月日的日期分量并按它们分组，然后将分组结果中的值映射到每个日期的数组数组。为了能够在最终结果中包含原始日期，使用元组作为字典的值类型

let groupedDates = Dictionary(grouping: dates
    .map { ([=10=],Calendar.current.dateComponents([.year, .month, .day], from: [=10=]))}, by: {[=10=].1})
    .mapValues {value in value.map {[=10=].0}}
    .values

从日期数组中获取日期数组

Get array of dates from an array of dates

nsdate

ios

swift