iOS swift3 Timer 的正确使用

因为iOS10有新方法，并且Timer与NSTimer改变了一些api:我们在swift3里面需要以下使用才好！

var timer:Timer!


 // 获取验证码
@IBAction func getVerifyCode(_ sender: AnyObject) {
    
    
    
    if timer == nil {
        
        if #available(iOS 10.0, *) {
            timer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true, block: { (timer) in
                
                self.countDown()
            })
        } else {
            // Fallback on earlier versions
            
            timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(countDown), userInfo: nil, repeats: true)
        }
        
        
        
    }else {
        
        
    }
    
}

func countDown(){
    
    print("11")
}

// 暂停

timer.fireDate = Date.distantFuture

// 重启

timer.fireDate = NSDate.init() as Date