IOS小组件实现时钟按秒刷新功能

let components = DateComponents(minute: 11, second: 14)
let futureDate = Calendar.current.date(byAdding: components, to: Date())!

Text(futureDate, style: .relative)
// Displays:
// 11 min, 14 sec

Text(futureDate, style: .offset)
// Displays:
// -11 minutes

let components = DateComponents(minute: 15)
let futureDate = Calendar.current.date(byAdding: components, to: Date())!

Text(futureDate, style: .timer)
// Displays:
// 15:00

// Absolute Date or Time
let components = DateComponents(year: 2020, month: 4, day: 1, hour: 9, minute: 41)
let aprilFirstDate = Calendar.current(components)!

Text(aprilFirstDate, style: .date)
Text("Date: \(aprilFirstDate, style: .date)")
Text("Time: \(aprilFirstDate, style: .time)")

// Displays:
// April 1, 2020
// Date: April 1, 2020
// Time: 9:41AM

let startComponents = DateComponents(hour: 9, minute: 30)
let startDate = Calendar.current.date(from: startComponents)!

let endComponents = DateComponents(hour: 14, minute: 45)
let endDate = Calendar.current.date(from: endComponents)!

Text(startDate ... endDate)
Text("The meeting will take place: \(startDate ... endDate)")

// Displays:
// 9:30AM-2:45PM
// The meeting will take place: 9:30AM-2:45PM

//获取当天开始的日期，给Date增加一个拓展方法
 extension Date {
    func getCurrentDayStart(_ isDayOf24Hours: Bool)-> Date {
        let calendar:Calendar = Calendar.current;
        let year = calendar.component(.year, from: self);
        let month = calendar.component(.month, from: self);
        let day = calendar.component(.day, from: self);
    
        let components = DateComponents(year: year, month: month, day: day, hour: 0, minute: 0, second: 0)
        return Calendar.current.date(from: components)!
    }
}
// 实现一天内的计时器
Text(Date().getCurrentDayStart(true), style: .timer)