swift中两个日期之间的计时器coutdown

let currentDate = Date()
let targetDate = // 目标日期

let calendar = Calendar.current
let components = calendar.dateComponents([.second], from: currentDate, to: targetDate)
let countdownSeconds = components.second ?? 0

var countdownTimer: Timer?

func startCountdown() {
    countdownTimer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(updateCountdown), userInfo: nil, repeats: true)
}

@objc func updateCountdown() {
    countdownSeconds -= 1
    
    // 更新UI或执行其他操作
    print("倒计时剩余时间：\(countdownSeconds)秒")
    
    if countdownSeconds <= 0 {
        stopCountdown()
    }
}

func stopCountdown() {
    countdownTimer?.invalidate()
    countdownTimer = nil
}