Start and End date of month in SwiftUI - ios

Question

How to get startDateOfMonth and endDateOfMonth based on selected date in SwiftUI?
I have found some answers for Swift (DateComponents), but couldn't make it work with SwiftUI.
Why I need this: I am going to use dynamic filters using predicate to filter all the data in the currently selected month (using custom control to switch months). But first I need to get the start and end dates per selected month.
EXAMPLE code:
ContentView.swift
import SwiftUI
struct ContentView: View {
#State var currentDate = Date()
// How to make startDateOfMonth and endDateOfMonth dependent on selected month?
#State private var startDateOfMonth = "1st January"
#State private var endDateOfMonth = "31st January"
var body: some View {
VStack {
DateView(date: $currentDate)
Text("\(currentDate)")
Text(startDateOfMonth)
Text(endDateOfMonth)
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
DateView.swift
import SwiftUI
struct DateView: View {
static let dateFormat: DateFormatter = {
let formatter = DateFormatter()
formatter.setLocalizedDateFormatFromTemplate("yyyy MMMM")
return formatter
}()
#Binding var date : Date
var body: some View {
HStack {
Image(systemName: "chevron.left")
.padding()
.onTapGesture {
print("Month -1")
self.changeDateBy(-1)
}
Spacer()
Text("\(date, formatter: Self.dateFormat)")
Spacer()
Image(systemName: "chevron.right")
.padding()
.onTapGesture {
print("Month +1")
self.changeDateBy(1)
}
}
.padding(EdgeInsets(top: 5, leading: 10, bottom: 5, trailing: 10))
.background(Color.yellow)
}
func changeDateBy(_ months: Int) {
if let date = Calendar.current.date(byAdding: .month, value: months, to: date) {
self.date = date
}
}
}
struct DateView_Previews: PreviewProvider {
struct BindingTestHolder: View {
#State var testItem: Date = Date()
var body: some View {
DateView(date: $testItem)
}
}
static var previews: some View {
BindingTestHolder()
}
}

Answer 1

I managed to solve it by the following implementation of ContentView
#State var currentDate = Date()
private var startDateOfMonth: String {
let components = Calendar.current.dateComponents([.year, .month], from: currentDate)
let startOfMonth = Calendar.current.date(from: components)!
return format(date: startOfMonth)
}
private var endDateOfMonth: String {
var components = Calendar.current.dateComponents([.year, .month], from: currentDate)
components.month = (components.month ?? 0) + 1
components.hour = (components.hour ?? 0) - 1
let endOfMonth = Calendar.current.date(from: components)!
return format(date: endOfMonth)
}
var body: some View {
VStack {
DateView(date: $currentDate)
Text("\(currentDate)")
Text(startDateOfMonth)
Text(endDateOfMonth)
}
}
private func format(date: Date) -> String {
let dateFormatter = DateFormatter()
dateFormatter.dateStyle = .medium
return dateFormatter.string(from: date)
}
Because currentDate is changed by DateView through Binding the body computed property will be invoked thus startDateOfMonth and endDateOfMonth computed properties will return the updated values.