In addition to UITableViewDelegate and UITableViewDataSource, a third protocol exists that you can implement to improve your table view's performance. It's called UITableViewDataSourcePrefetching and you can use it to enhance your data source. If your data source performs some complex task, such as retrieving and decoding an image, it could slow down the performance of your table view if this task is performed at the moment the table view wants to retrieve a cell. Performing this operation a little bit sooner than that can positively impact your app in those cases.
Since Hello-Contacts currently decodes contact images for its cells, it makes sense to implement prefetching to make sure the scrolling performance ...
