how to use UIPicker dataSource - swift

Question

I use the Xcode 8 and swift 2.3, but I met a problem the UIPickerView.dataSource = (self as! UIPickerViewDataSource) doesn't work when I try to use func of UIPicker, this is my code:
import UIKit
class ViewController: UIViewController {
let Num = ["1","2","3","4","5","6"]
#IBOutlet weak var UIPicker: UIPickerView!
override func viewDidLoad() {
super.viewDidLoad()
func numberOfRows(inComponent component: Int) -> Int {return 1}
func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {return Num.count}
func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {return Num[row]}
UIPicker.dataSource = (self as! UIPickerViewDataSource)
UIPicker.delegate = (self as! UIPickerViewDelegate)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
When I run my code, Xcode warning the code:
Could not cast value of type 'test.ViewController' (0x1000bd8c0) to
'UIPickerViewDataSource' (0x1ab289738). 2016-06-29 15:33:35.079300
test[474:98176] Could not cast value of type 'test.ViewController'
(0x1000bd8c0) to 'UIPickerViewDataSource' (0x1ab289738).

Answer 1

Add UIPickerViewDataSource and UIPickerViewDelegate to the class declaration:
class ViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate
and don't use type casting using self:
override func viewDidLoad() {
super.viewDidLoad()
UIPicker.dataSource = self
UIPicker.delegate = self
}
Also you must move your methods out of viewDidLoad function, and correct them a bit:
func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {return 1}
func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {return Num.count}
func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {return Num[row]}
Note that I highly recommend you to rename your Num and UIPicker properties to num and picker, so you will not mix them with class names
Upd: full ViewController code:
class ViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate {
let Num = ["1","2","3","4","5","6"]
#IBOutlet weak var UIPicker: UIPickerView!
override func viewDidLoad() {
super.viewDidLoad()
UIPicker.dataSource = self
UIPicker.delegate = self
}
func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {return 1}
func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {return Num.count}
func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {return Num[row]}
}

Answer 2

import Foundation
import UIKit
class MakeReferralViewController: UITableViewController,UIPickerViewDelegate, UITextFieldDelegate,UIPickerViewDataSource {
#IBOutlet weak var makeReferralScroll: UIScrollView!
#IBOutlet weak var userTitleUITextView: UITextField!
var pickerData = ["Mr.", "Ms.", "Mrs.", "Miss."];
var picker = UIPickerView()
override func viewDidLoad() {
super.viewDidLoad()
picker.delegate = self
picker.dataSource = self
userTitleUITextView.inputView = picker
// Do any additional setup after loading the view, typically from a nib.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func textFieldDidBeginEditing(_ textField: UITextField) {
makeReferralScroll.setContentOffset(CGPoint(x:0,y:250), animated: true)
}
func textFieldShouldReturn(_ textField: UITextField) -> Bool {
textField.resignFirstResponder()
return true;
}
#available(iOS 10.0, *)
func textFieldDidEndEditing(_ textField: UITextField, reason: UITextFieldDidEndEditingReason) {
makeReferralScroll.setContentOffset(CGPoint(x:0,y:0), animated: true)
}
func numberOfComponents(in pickerView: UIPickerView) -> Int {
return 1
}
public func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
return pickerData.count
}
//MARK: Delegate
func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
return pickerData[row]
}
func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
userTitleUITextView.text = pickerData[row]
}
}