How to group array of dates by months in swift? - ios

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]()

Answer 1

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)
}

Answer 2

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)

Answer 3

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)