按月分组 Swift 日期数组

Question

我有一个 Swift 日期数组：

[date1, date2, date3, ..., dateN]

我想按月份对这些日期进行分组：

[
    [date1, date2],
    [date3],
    ...
    [dateN],
]

一个月的所有日子都应该在同一个月份数组中。

如何按月对日期数组进行分组，无论是函数式还是命令式？

Answer 1

斯威夫特 4

这就是我的做法：

extension Date {
    
    var month: Int {
        return Calendar.current.component(.month, from: self)
    }
    
}

// some random arbitrary dates
let rawDates = [Date(), Date().addingTimeInterval(100000.0), Date().addingTimeInterval(100000000.0)]
// the desired format
var sortedDatesByMonth: [[Date]] = []

// a filter to filter months by a given integer, you could also pull rawDates out of the equation here, to make it pure functional
let filterDatesByMonth = { month in rawDates.filter { $0.month == month } }
// loop through the months in a calendar and for every month filter the dates and append them to the array
(1...12).forEach { sortedDatesByMonth.append(filterDatesByMonth($0)) }

在 Xcode 9.2 操场上测试和工作。

输出

[[], [], [2018-03-21 12:29:10 +0000, 2018-03-22 16:15:50 +0000], [], [2021-05-21 22:15:50 +0000], [], [], [], [], [], [], []]

用于假设的 AppointmentObject

extension Date {
    
    var month: Int {
        return Calendar.current.component(.month, from: self)
    }
    
}

// some random arbitrary dates
let appointments = [AppointmentObject(), AppointmentObject(), AppointmentObject()]
// the desired format
var sortedAppointmentsByFromMonth: [[AppointmentObject]] = []

// a filter to filter months by a given integer, you could also pull rawDates out of the equation here, to make it pure functional
let filterFromDatesByMonth = { month in appointments.filter { $0.from.month == month } }
// loop through the months in a calendar and for every month filter the dates and append them to the array
(1...12).forEach { sortedAppointmentsByFromMonth.append(filterFromDatesByMonth($0)) }

替代方案

不是您问题的直接答案，但也可能是您问题的可行解决方案。许多人正确地指出了Dictionary 类的存在。使用上面提到的Date 扩展，你也可以这样做：

Dictionary(grouping: rawDates) {$0.month}

输出

您的键现在是月份指示符（5 月和 3 月 3 日）

[5: [2021-05-21 22:46:44 +0000], 3: [2018-03-21 13:00:04 +0000, 2018-03-22 16:46:44 +0000]]