// this is the cell height cache; obviously you don't want a static size array in production
var itemHeights = [CGFloat](count: 1000, repeatedValue: UITableViewAutomaticDimension) 

func tableView(tableView: UITableView, willDisplayCell cell: UITableViewCell, forRowAtIndexPath indexPath: NSIndexPath) {
  if itemHeights[indexPath.row] == UITableViewAutomaticDimension {
    itemHeights[indexPath.row] = cell.bounds.height
  }
  // fetch more cells, etc.
}

func tableView(tableView: UITableView, estimatedHeightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
  return itemHeights[indexPath.row]
}

但是没有解决动态高度，如某个文案 有一个less和more点击的