 
 class CountDownTask: Task {
 
-	/// a number counting down from(起始计数)
+	/// a number counting down from
 	private var from: Int?
 
-	/// a number count down to, default is 0(终止计数, 默认为0)
+	/// a number count down to, default is 0
 	private var to: Int = 0
 
-	/// count down interval in second, default is 1.0(计数间隔, 单位秒, 默认为1.0)
+	/// count down interval in second, default is 1.0
 	private var interval: Double = 1.0
 
-	/// a block called in progress of counting down(倒计时过程中的回调)
+	/// a block called in progress of counting down
 	private var at: ((Int) -> Void)?
 
-	/// a block called after counting down finished(倒计时结束时的回调)
+	/// a block called after counting down finished
 	private var finish: (() -> Void)?
 
-	/// a concurrent queue on which the task is attached(计时任务执行的队列)
+	/// a concurrent queue on which the task is attached
 	private var queue: DispatchQueue?
 
 	/// delegate


	/**
	designed initializer
	(快速构造方法)
	- parameter identifier: task identifier(任务ID)
	- parameter from:       a number counting down from(起始计数)
	- parameter to:         a number count down to, default is 0(终止计数, 默认为0)
	- parameter interval:   count down interval in second, default is 1.0(计数间隔, 单位秒, 默认为1.0)
	- parameter at:         a block called in progress of counting down(倒计时过程中的回调)
	- parameter finish:     a block called after counting down finished(倒计时结束时的回调)
	- returns: a CountDownTask instance(返回一个倒数计时任务实例)
	*/
	convenience init(identifier: String, from: Int, to: Int = 0, interval: Double = 1.0, at: ((at: Int) -> Void)?, finish: (() -> Void)?) {
		self.init()


	/**
	counting down finished
	*/
	internal func stopCountDown() {
		DispatchQueue.main.async {
			self.finish?()
			self.delegate?.task(didFinish: self)
		}
	}

