use picker

In view controller:

(1) conform protocol: UIPickerViewDelegate, UIPickerViewDataSource

(2) add an outlet for UIPickerView

(3) implement two picker data source method

numberOfComponentInPickerView &

pickerView: numberOfRowsInComponent

In IB:

(1) add picker view to view

(2) connect file's owner's outlet pickerView to pickerView

(3) connect pickerView's outlet dataSource & delegate to file's owner