title: How to design and create a GridView using UIScrollView or UITableView
body: <p>I think GridView is a very common view in many situation. As a beginner in iOS, I just wonder why iOS didn't provide a GridView class.
  So here's my question, how to design and create a GridView using UIScrollView or UITableView?
  or is there some other solution to create a GridView?</p>