How to group array of dates by months in swift?

Question

I am working on a scheduling app. I want all the dates of the given months I am not able to group dates by months that is what I tried but I want a different expected result

extension Date {
    static func dates(from fromDate: Date, to toDate: Date) -> [Date] {
        var dates: [Date] = []
        var date = fromDate

        while date <= toDate {
            dates.append(date)
            guard let newDate = Calendar.current.date(byAdding: .day, value: 1, to: date) else { break }
            date = newDate
        }
        return dates
    }
    var month: Int {
        return Calendar.current.component(.month, from: self)
    }
}

let fromDate = Calendar.current.date(byAdding: .day, value: 30, to: Date())
let datesBetweenArray = Date.dates(from: Date(), to: fromDate!)
var sortedDatesByMonth: [[Date]] = []
let filterDatesByMonth = { month in datesBetweenArray.filter { $0.month == month } }
(1...12).forEach { sortedDatesByMonth.append(filterDatesByMonth($0)) }

The result is in this format [[], [], [], [], [], [], [2019-07-31 03:51:19 +0000],……., [], [], [], []]

This kinda result I want expecting

struct ScheduleDates {
    var month: String
    var dates: [Date]

    init(month: String, dates: [Date]) {
        self.month = month
        self.dates = dates
    }
}
var sections = [ScheduleDates]()

struct names should be CapitalizedCamelCase, so it should be struct ScheduleDates { // stuff } — Adrian
– Adrian, Commented Jul 31, 2019 at 4:19
Do you want to generate this from an array of the structs that you defined or do you want to feed it an array of dates? — Adrian
– Adrian, Commented Jul 31, 2019 at 5:09
@Adrian In the above code, it is in Array of Array format but I want the result on the format of Array of the struct. — Gitz
– Gitz, Commented Jul 31, 2019 at 5:12
I posted below how to do what you describe along with some suggestions if you're going to be displaying this information in something like a UITableView or UICollectionView. — Adrian
– Adrian, Commented Jul 31, 2019 at 5:59

May Rest in Peace · Accepted Answer · 2019-07-31 06:19:29Z

5

If you want to group your dates by month you can create a Dictionary like this:

Dictionary(grouping: datesBetweenArray, by: { $0.month })

This results in the following output of the format [Int: [Date]]

The key of the dictionary will be your month.

Now you can initialize your scheduleDates struct by looping through this dictionary in this way:

var sections = Dictionary(grouping: datesBetweenArray,
                          by: ({$0.month}))
    .map { tuple in
        ScheduleDates(month: String(tuple.0), dates: tuple.1)
}

edited Jul 31, 2019 at 6:19

answered Jul 31, 2019 at 4:15

May Rest in Peace

2,2272 gold badges26 silver badges38 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Gitz Over a year ago

But in Dictionary the sequence might change white updating it as I know.. that's why using Array.

May Rest in Peace Over a year ago

@Gitz I didn't understand that the sequence might change. My understanding is that you have an array of dates and you want to convert it to an array of ScheduleDates, right ?

Gitz Over a year ago

How can I loop to the dictionary for 'ScheduleDates' Array

May Rest in Peace Over a year ago

@Gitz Edited the answer to add code for looping through dict and creating [ScheduleDates]

Adrian · Accepted Answer · 2019-07-31 06:15:41Z

Here's the code for a Playground

I think your structs should probably be Int values for the months, as when you go to populate something like a tableview, it'll be a PITA to re-order months if you've got them as Strings.

struct ScheduleDates {
    var month: String
    var dates: [Date]
}

Anyway, here's the extension I wrote based on what you provided. I frankly think you should return a dictionary with an Int as the key and an array of Dates as the value, but here's what you wanted...

I used Dictionary(grouping:by:) to construct a dictionary from an array of dates.

extension Date {
    static func dateDictionary(from arrayOfDates: [Date]) -> [String: [Date]] {
        // declare a dictionary
        return Dictionary(grouping: arrayOfDates) { date -> String in
            // get the month as an int
            let monthAsInt = Calendar.current.dateComponents([.month], from: date).month
            // convert the int to a string...i think you probably want to return an int value and do the month conversion in your tableview or collection view
            let monthName = DateFormatter().monthSymbols[(monthAsInt ?? 0) - 1]
            // return the month string
            return monthName
        }
    }
}

Here's a utility method I wrote to generate data while I figured out how to do it. If you're going to be in production, don't force unwrap stuff as I did here.

// Utility method to generate dates
func createDate(month: Int, day: Int, year: Int) -> Date? {
    var components = DateComponents()
    components.month = month
    components.day = day
    components.year = year

    return Calendar.current.date(from: components)!
}

Below is how I generated an array of sample dates to experiment.

// generate array of sample dates
let dateArray: [Date] = {
    let months = Array(1...12)
    let days = Array(1...31)
    let years = [2019]

    var dateArray: [Date] = []

    while dateArray.count < 100 {
        let randomMonth = months.randomElement()
        let randomDay = days.randomElement()
        let randomYear = years.randomElement()

        if let month = randomMonth,
            let day = randomDay,
            let year = randomYear,
            let date = createDate(month: month,
                                  day: day,
                                  year: year) {
            dateArray.append(date)
        }
    }

    return dateArray
}()

let monthDictionary = Date.dateDictionary(from: dateArray)

var arrayOfStructs: [ScheduleDates] = []

monthDictionary.keys.forEach { key in
    let scheduleDate = ScheduleDates(month: key,
                                     dates: monthDictionary[key] ?? [])
    arrayOfStruct.append(scheduleDate)
}

print(arrayOfStructs)

Thanks for your reply. This answer is exactly what I am looking for. What if I take Int instead of String ?
Here's a GitHub repo with the code updated from month string to months as Ints. github.com/AdrianBinDC/DatesByMonth

4 revs, 2 users 73% · Accepted Answer · 2019-07-31 05:21:34Z

You can use my code. Which i write to adapt your case.

let fromDate = Calendar.current.date(byAdding: .day, value: 30, to: Date())
let datesBetweenArray = Date.dates(from: Date(), to: fromDate!)
if datesBetweenArray.count <= 1 {
    print(datesBetweenArray)
}
var sortedDatesByMonth: [[Date]] = []
var tempMonth = datesBetweenArray[0].month
var dates: [Date] = []
for i in 0..<datesBetweenArray.count {

    if tempMonth == datesBetweenArray[i].month {
        dates.append(datesBetweenArray[i])
        if i == datesBetweenArray.count - 1 {
            sortedDatesByMonth.append(dates)
        }
    } else {
        sortedDatesByMonth.append(dates)
        tempMonth = datesBetweenArray[i].month
        dates.removeAll()
        dates.append(datesBetweenArray[i])
    }
}
print(sortedDatesByMonth.count)
print(sortedDatesByMonth)

Collectives™ on Stack Overflow

How to group array of dates by months in swift?

3 Answers 3

4 Comments

2 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

4 Comments

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related