swift中的跑马灯实现（导航栏）

首先是懒加载了runLabel：

  private lazy var runLabel : UILabel={
      let label = UILabel()
      label.sizeToFit()
    
     label.font = UIFont(name: kMyFontName, size: kFontSize14)
     label.textColor = UIColor.blackColor()
     return label
 }()

然后在viewDidLoad中实现addsubView方法：

    /// 跑马灯
    self.navigationItem.titleView?.addSubview(runLabel)
    //设置label的原始位置
    runLabel.frame.origin.x = kScreenWidth

    
    UIView.beginAnimations(self.productName, context: nil)
    UIView.setAnimationDuration(16)
    UIView.setAnimationCurve(UIViewAnimationCurve.Linear)
    UIView.setAnimationDelegate(self)
    UIView.setAnimationRepeatCount(999999)
    
    runLabel.frame.origin.x = -runLabel.frame.size.width
    UIView .commitAnimations()

另外如果文字过长的话建议直接计算文字宽度（做个简单的分类即可）

extension String {
  func getTitleW() -> CGFloat{
     /// 计算文字宽度
     var dict:[String:AnyObject] = [:]
      dict[NSFontAttributeName] = UIFont(name: kMyFontName, size:   kFontSize14)
          return NSString(string:     self).boundingRectWithSize(CGSizeMake(999, 14), options: NSStringDrawingOptions.UsesLineFragmentOrigin, attributes: dict, context: nil).size.width + 24

    }
}