get days in given date's month

a.swift

import Foundation


struct MCalendarDate {
    let weekOfYear: Int
    let weekday: Int
    let day: Int
    let month: Int
    let year: Int
    let date: Date
}

struct MCalendarWeek {
    let weekOfYear: Int
    var days: [MCalendarDay]
}

struct MCalendarDay {
    let weekday: Int
    let day: Int
    let month: Int
    let year: Int
    let date: Date
}

let date = Date()


var calendar = Calendar(identifier: .iso8601)
calendar.locale = Locale(identifier: "tr_TR")


var days: [MCalendarDate] = []
var ds: [MCalendarWeek] = []

var firstDayComponents = calendar.dateComponents([.year, .month], from: date)
let firstDay = calendar.date(from: firstDayComponents)!
let range = calendar.range(of: .day, in: .month, for: firstDay)!

var checkOfWeekOfYear = -1
var calWeek: MCalendarWeek?

for index in 0..<range.count {
    let d = calendar.date(byAdding: .day, value: index, to: firstDay)!
    let weekOfYear = calendar.component(.weekOfYear, from: d)
    let weekday = (calendar.component(.weekday, from: d) - 1 + 6) % 7
    let day = calendar.component(.day, from: d)
    let month = calendar.component(.month, from: d)
    let year = calendar.component(.year, from: d)
    days.append(MCalendarDate(weekOfYear: weekOfYear, weekday: weekday, day: day, month: month, year: year, date: d))
    
    if checkOfWeekOfYear != weekOfYear {
        checkOfWeekOfYear = weekOfYear
        
        if calWeek != nil {
            ds.append(calWeek!)
            calWeek = nil
        }
        
        calWeek = MCalendarWeek(weekOfYear: weekOfYear, days: [])
    }
    
    calWeek?.days.append(MCalendarDay(weekday: weekday, day: day, month: month, year: year, date: d))
}

for d in ds {
    print("Week of year: \(d.weekOfYear)")
    for dd in d.days {
        print(dd)
    }
}

//for d in days {
//    print(d)
//}