This is an implementation of a calendar component for iOS written in Swift 4.0. It features both vertical and horizontal layout (and scrolling) and the display of native calendar events.
- iOS 8.0+
- XCode 9.0+
- Swift 4.0 +
pod 'KDCalendar', '~> 1.2'
The files needed to be included are in the CalendarView subfolder of this project.
The calendar is a UIView and can be added either programmatically or via a XIB/Storyboard.
It needs a delegate and data source that comply with:
protocol CalendarViewDataSource {
func startDate() -> NSDate // UTC Date
func endDate() -> NSDate // UTC Date
}
protocol CalendarViewDelegate {
func calendar(_ calendar : CalendarView, canSelectDate date : Date) -> Bool /* default implementation */
func calendar(_ calendar : CalendarView, didScrollToMonth date : Date) -> Void
func calendar(_ calendar : CalendarView, didSelectDate date : Date, withEvents events: [CalendarEvent]) -> Void
func calendar(_ calendar : CalendarView, didDeselectDate date : Date) -> Void /* default implementation */
}The data source will provide the start date and the end date of the calendar. The methods have a default implementation that will return Date() resulting in a single-page calendar displaying the current month.
The delegate responds to events such as scroll and selection of specific dates.
You would want to implement the delegate functions inside your view controller and as they appear in the example project.
Say you want to be able to scroll 3 months in the past, then:
func startDate() -> Date {
var dateComponents = DateComponents()
dateComponents.month = -3
let today = Date()
let threeMonthsAgo = self.calendarView.calendar.date(byAdding: dateComponents, to: today)
return threeMonthsAgo
}You probably still want the calendar to open in today's date, so in this case do:
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let today = Date()
self.calendarView.setDisplayDate(today, animated: false)
}Say you want tomorrow to be selected for some reason:
// can be in the viewDidAppear
let today = Date()
if let tomorrow = self.calendarView.calendar.date(byAdding: tomorrowComponents, to: today) {
self.calendarView.selectDate(tomorrow)
}The calendar supports the selection of multiple dates. You can select a date either by clicking on a cell or by selecting it programmatically as:
self.calendarView.selectDate(date)Similarly you can deselect
self.calendarView.deselectDate(date)You can get all the dates that where selected, either manually or programatically by
self.calendarView.selectedDatesThe calendar supports the two basic layouts set inside the direction property as .horizontal or .vertical.
calendarView.direction = .horizontalThe look of this calendar component is based on a small set of variables set in CalanderView.Style.
struct Style {
enum CellShapeOptions {
case Round
case Square
case Bevel(CGFloat)
}
static var CellColorDefault : UIColor
static var CellColorToday : UIColor
static var CellTextColorDefault : UIColor
static var CellTextColorToday : UIColor
static var CellBorderColor : UIColor
static var CellBorderWidth : CGFloat
static var CellShape : CellShapeOptions
static var CellEventColor : UIColor
static var HeaderFontName : String
static var HeaderTextColor : UIColor
}The CellShape will define whether the dates are displayed in a circle or square with bevel or not.
This component has the ability to fetch events from the system's EKEventStore which is syncronised with the native calendar provided in iOS.
EventsLoader.load(from: self.startDate(), to: self.endDate()) { // (events:[CalendarEvent]?) in
if events = $0 {
self.calendarView.events = events
} else {
// notify that access was not access not granted
}
}The code will pop an alert view to ask the user if he will grant access to this app to access the calendar, if it is granted we can pass the events to the CalendarView, otherwise we get a nil and notify the app about the denial.
Calculating calendar dates can be pretty complicated. This is because time is an absolute scalar value while dates are a fluid human construct. Timezones are arbitrary geopolitical areas and daylight savings times can change according to government decision. The best way out of this is to calculate everything in UTC (which is the same as GTM for what we are concerned). So, the startDate and the endDatet comming from the delegate should all be in UTC (+0000) time.