update view daily at particular time, or any other date-based interval

DateComponentsTimelineSchedule.swift

import SwiftUI

struct DateComponentsTimelineSchedule: TimelineSchedule {
    let components: DateComponents
    let calendar: Calendar
    let matchingPolicy: Calendar.MatchingPolicy
    
    init(
        components: DateComponents,
        calendar: Calendar = .current,
        matchingPolicy: Calendar.MatchingPolicy = .nextTime
    ) {
        self.components = components
        self.calendar = calendar
        self.matchingPolicy = matchingPolicy
    }
    
    func entries(from startDate: Date, mode: TimelineScheduleMode) -> DateComponentsSequence {
        DateComponentsSequence(
            startDate: startDate,
            components: components,
            calendar: calendar,
            matchingPolicy: matchingPolicy
        )
    }
    
    struct DateComponentsSequence: Sequence, IteratorProtocol {
        var nextDate: Date?
        let components: DateComponents
        let calendar: Calendar
        let matchingPolicy: Calendar.MatchingPolicy
        
        init(
            startDate: Date,
            components: DateComponents,
            calendar: Calendar,
            matchingPolicy: Calendar.MatchingPolicy
        ) {
            self.components = components
            self.calendar = calendar
            self.matchingPolicy = matchingPolicy
            
            // Find the most recent occurrence by searching backward from now
            // This ensures we always start from a valid point, even if it's in the past
            self.nextDate = calendar.nextDate(
                after: startDate,
                matching: components,
                matchingPolicy: matchingPolicy,
                direction: .backward
            )
        }
        
        mutating func next() -> Date? {
            guard let current = nextDate else { return nil }
            
            // Find next occurrence after current
            nextDate = calendar.nextDate(
                after: current,
                matching: components,
                matchingPolicy: matchingPolicy
            )
            
            return current
        }
    }
}

extension TimelineSchedule where Self == DateComponentsTimelineSchedule {
    /// A schedule that updates at dates matching the given DateComponents
    static func dateComponents(
        _ components: DateComponents,
        calendar: Calendar,
        matchingPolicy: Calendar.MatchingPolicy = .nextTime
    ) -> DateComponentsTimelineSchedule {
        DateComponentsTimelineSchedule(
            components: components,
            calendar: calendar,
            matchingPolicy: matchingPolicy
        )
    }
    
    /// A schedule that updates daily at the specified time
    static func daily(at hour: Int, minute: Int = 0, calendar: Calendar) -> DateComponentsTimelineSchedule {
        var components = DateComponents()
        components.hour = hour
        components.minute = minute
        components.second = 0
        
        return DateComponentsTimelineSchedule(components: components, calendar: calendar)
    }
}