I think what you're asking is that you want 4 UIPickerView controls on one UIView. I'm assuming you can put each one in a UITableView, but I would highly suggest you don't.
One UIPickerView takes up roughly 3/4 of the screen (in height). If you have multiple pickers, how does the iPhone know how to scroll down as opposed to "spinning" the picker? It is the same swipe action.
My recommendation is that you have a UITableView with 4 rows. When the user selects a row, your app should navigate to a new view with one UIPickerView. You can have a "save" or "cancel" button to return back to the table view. This would be more in conformance to the Apple style guides.