override func drawRect(rect: CGRect) {
      var aPath = UIBezierPath()

      aPath.moveToPoint(CGPoint(x:/*Put starting Location*/,y:/*Put starting Location*/))

      aPath.addLineToPoint(CGPoint(x:/*Put Next Location*/,y:/*Put Next Location*/))

      //Keep using the method addLineToPoint until you get to the one where about to close the path

      aPath.closePath()

      //If you want to stroke it with a red color
      UIColor.redColor().set()
      aPath.stroke()
      //If you want to fill it as well 
      aPath.fill()
}

确保将此代码放在drawRect中.就像上面的例子一样.

如果需要更新图形,只需调用setNeedsDisplay()即可更新.