SwiftUI Calendar view using LazyVGrid

Calendar.swift

import SwiftUI

extension Calendar {
    func generateDates(
        inside interval: DateInterval,
        matching components: DateComponents
    ) -> [Date] {
        var dates: [Date] = []
        dates.append(interval.start)

        enumerateDates(
            startingAfter: interval.start,
            matching: components,
            matchingPolicy: .nextTime
        ) { date, _, stop in
            if let date = date {
                if date < interval.end {
                    dates.append(date)
                } else {
                    stop = true
                }
            }
        }

        return dates
    }
}

extension DateFormatter {
    static let monthAndYear: DateFormatter = {
        let formatter = DateFormatter()
        formatter.setLocalizedDateFormatFromTemplate("MMMM yyyy")
        return formatter
    }()
}

struct EquatableCalendarView<DateView: View, Value: Equatable>: View, Equatable {
    static func == (
        lhs: EquatableCalendarView<DateView, Value>,
        rhs: EquatableCalendarView<DateView, Value>
    ) -> Bool {
        lhs.interval == rhs.interval && lhs.value == rhs.value && lhs.showHeaders == rhs.showHeaders
    }
    
    let interval: DateInterval
    let value: Value
    let showHeaders: Bool
    let onHeaderAppear: (Date) -> Void
    let content: (Date) -> DateView
    
    init(
        interval: DateInterval,
        value: Value,
        showHeaders: Bool = true,
        onHeaderAppear: @escaping (Date) -> Void = { _ in },
        @ViewBuilder content: @escaping (Date) -> DateView
    ) {
        self.interval = interval
        self.value = value
        self.showHeaders = showHeaders
        self.onHeaderAppear = onHeaderAppear
        self.content = content
    }
    
    var body: some View {
        CalendarView(
            interval: interval,
            showHeaders: showHeaders,
            onHeaderAppear: onHeaderAppear
        ) { date in
            content(date)
        }
    }
}

struct CalendarView<DateView>: View where DateView: View {
    let interval: DateInterval
    let showHeaders: Bool
    let onHeaderAppear: (Date) -> Void
    let content: (Date) -> DateView

    @Environment(\.sizeCategory) private var contentSize
    @Environment(\.calendar) private var calendar
    @State private var months: [Date] = []
    @State private var days: [Date: [Date]] = [:]

    private var columns: [GridItem] {
        let spacing: CGFloat = contentSize.isAccessibilityCategory ? 2 : 8
        return Array(repeating: GridItem(spacing: spacing), count: 7)
    }

    var body: some View {
        LazyVGrid(columns: columns) {
            ForEach(months, id: \.self) { month in
                Section(header: header(for: month)) {
                    ForEach(days[month, default: []], id: \.self) { date in
                        if calendar.isDate(date, equalTo: month, toGranularity: .month) {
                            content(date).id(date)
                        } else {
                            content(date).hidden()
                        }
                    }
                }
            }
        }
        .onAppear {
            months = calendar.generateDates(
                inside: interval,
                matching: DateComponents(day: 1, hour: 0, minute: 0, second: 0)
            )
            
            days = months.reduce(into: [:]) { current, month in
                guard
                    let monthInterval = calendar.dateInterval(of: .month, for: month),
                    let monthFirstWeek = calendar.dateInterval(of: .weekOfMonth, for: monthInterval.start),
                    let monthLastWeek = calendar.dateInterval(of: .weekOfMonth, for: monthInterval.end)
                else { return }
                
                current[month] = calendar.generateDates(
                    inside: DateInterval(start: monthFirstWeek.start, end: monthLastWeek.end),
                    matching: DateComponents(hour: 0, minute: 0, second: 0)
                )
            }
        }
    }

    private func header(for month: Date) -> some View {
        Group {
            if showHeaders {
                Text(DateFormatter.monthAndYear.string(from: month))
                    .font(.title)
                    .padding()
            }
        }
        .onAppear { onHeaderAppear(month) }
    }
}

Hi you guys.
Do you know how I can draw a background like image below?

thank you @mecid for this gist,

I even built an Calendar app using your component

https://github.com/vinhnx/Clendar

Thank you for sharing. It's changed my mindset about my calendar before. I had to think about the calendar, it's faster if you use the library
But with swiftui, it's more flexible. It doesn't take as much time as I thought

• I personally think it should become a repository for more contributions, updates, and migration. Wait for it.
  @mecid

From the idea of this gist. I had created an example for a Calendar that can be customized more. Thank you.
Hope this helps someone.
https://github.com/iletai/SwiftUICalendarView

@mecid, @filimo, @funkenstrahlen How can I enable horizontal scrolling for this custom table calendar? Currently, when I scroll horizontally, it navigates to the next or previous month. I've been searching for a solution so far. If anyone knows the answer, please share it with me. Thank you.