A Navigation Controller manages a stack of view controllers to provide a drill-down interface for hierarchical content. The view hierarchy of a navigation controller is self contained. It is composed of views that the navigation controller manages directly and views that are managed by CONTENT VIEW CONTROLLERS you provide. Each content view controller manages a distinct view hierarchy, and the navigation controller coordinates the navigation between these view hierarchies.
// add method:
delete the row from the data source:
Style: UIBarButtonItem style Bordered target: self
Action : @ selector (back)];
-(NSInteger) number of components in picker view: