ObservableObject with DatePicker in SwiftUI - swiftui

Question

Can you help me with the following source code:
import SwiftUI
class DateHandler {
/* create a variable
Class to manage start date and end date
*/
var date1 : Date {
didSet{
print("StartDate: \(date1)")
}
}
var date2 : Date {
didSet{
print("EndDate: \(date2)")
}
}
var startDate:Date {
get{
return date1
}
set(newValue){
date1 = toLocalTime(date: newValue)
}
}
var endDate:Date {
get{
return date2
}
set(newValue){
date2 = addOneDay(date: toLocalTime(date: newValue))
}
}
init(){
self.date1 = Date()
self.date2 = Date()
}
//Customize time zone
func toLocalTime(date : Date) -> Date {
//Auswahl der aktuellen Kalender
let calendar = Calendar.current
//Auswahl der Zeitzone
let timezone = TimeZone.current
//Bestimmen Anzahl Sekunden zwischen Zeitzone und GMT
let seconds = TimeInterval(timezone.secondsFromGMT(for: date))
//Anpassen des eingelesenen Werts
let newDate = calendar.date(bySettingHour: 00, minute: 00, second: 00, of: date)
let dateLocalTimezone = Date(timeInterval: seconds, since: newDate!)
return dateLocalTimezone
}
func addOneDay(date : Date) -> Date {
let tomorrow = Calendar.current.date(byAdding: .day, value: 1, to: date)
return tomorrow!
}
}
//Class to use DateHandler() as a ObservableObject
class DateHandlerHelper : ObservableObject{
#Published var dateHandler = DateHandler()
}
struct ContentView: View {
#ObservedObject var dateHandlerHelper = DateHandlerHelper()
#State var startDateHelper = Date()
#State var endDateHelper = Date()
var body: some View {
DatePicker("Date1", selection: $startDateHelper)
.onAppear(perform: {
print("onAppear")
dateHandlerHelper.dateHandler.startDate = startDateHelper
print(dateHandlerHelper.dateHandler.startDate)
})
.onChange(of: startDateHelper) { newValue in
print("onChange")
dateHandlerHelper.dateHandler.startDate = newValue
if newValue > endDateHelper{
print("Correction Date 1")
startDateHelper = endDateHelper
dateHandlerHelper.dateHandler.startDate = endDateHelper
}
print(dateHandlerHelper.dateHandler.startDate)
}
DatePicker("Date2", selection: $endDateHelper)
.onAppear(perform: {
dateHandlerHelper.dateHandler.endDate = endDateHelper
print(dateHandlerHelper.dateHandler.endDate)
})
.onChange(of: endDateHelper) { newValue in
print("onChange")
dateHandlerHelper.dateHandler.endDate = newValue
print(dateHandlerHelper.dateHandler.endDate)
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
I have a view with two DatePickers to select a start date and an end date. For the start date and end date there is the class DateHandler.
I want to handle the DateHandler class as an ObservableObject. Because of the getter/setter function used, I can only address the DateHandler class indirectly through the DateHandlerHelper class. Is there a better/simpler way here?
If I address the variables dateHandlerHelper.dateHandler.startDate and dateHandlerHelper.dateHandler.endDate directly via the DatePickers, I can change the values, but the DatePickers themselves are not updated. For this reason I have introduced the variables startDateHelper and endDateHelper in the view. Do you have any idea how I can do this differently to save me the variables?

Answer 1

I don't see why you need to do those date calculations every time instead I changed so that they are done once when the DateHelper class is initialized.
class DateHandler: ObservableObject {
#Published var startDate: Date
#Published var endDate: Date
init(){
startDate = Self.toLocalTime(date: .now)
//I assume endDate also should be adjusted for local time?
let date = Self.addOneDay(date: .now)
endDate = Self.toLocalTime(date: date)
}
private static func toLocalTime(date : Date) -> Date {
// removed for brevity
}
private static func addOneDay(date : Date) -> Date {
// removed for brevity
}
}
And then the view would be much simpler
struct ContentView: View {
#ObservedObject var dateHandler = DateHandler()
var body: some View {
VStack {
DatePicker("Date1", selection: $dateHandler.startDate)
DatePicker("Date2", selection: $dateHandler.endDate)
}
}
}

Answer 2

This seems to be the right way:
class DateModel : ObservableObject{
var date1 : Date{
didSet{
print(date1)
}
}
var date2 : Date{
didSet{
print(date2)
}
}
var startDate:Date {
get{
return date1
}
set(newValue){
date1 = toLocalTime(date: newValue)
startDateString = date1.toString()
print(startDateString)
}
}
var endDate:Date {
get{
return date2
}
set(newValue){
date2 = toLocalTime(date: newValue)
}
}
init(){
self.date1 = Date()
self.date2 = Date()
}
//Customize time zone
func toLocalTime(date : Date) -> Date {
//Selection of the current calendar
let calendar = Calendar.current
//Time zone selection
let timezone = TimeZone.current
//Determine number of seconds between time zone and GMT
let seconds = TimeInterval(timezone.secondsFromGMT(for: date))
//Adjusting the input value
let newDate = calendar.date(bySettingHour: 00, minute: 00, second: 00, of: date)
let dateLocalTimezone = Date(timeInterval: seconds, since: newDate!)
return dateLocalTimezone
}
}
struct ContentView: View {
#ObservedObject var dateModel = DateModel()
var dateFormatter: DateFormatter {
let formatter = DateFormatter()
formatter.dateStyle = .long
return formatter
}
var body: some View {
Form{
Section{
DatePicker("start date", selection: $dateModel.startDate, displayedComponents: [.date]).onChange(of: dateModel.startDate) { newValue in
print(newValue.toString())
}
DatePicker("final date", selection: $dateModel.endDate, displayedComponents: [.date])
}
}
}
}