Picker view default row is not changing using swift 2

Question

I want to change picker view default selected row programmatically by reading data from core data and checking them. I used select row and didselectrow but in action it just change the value of the picker view not it's visual selected row! which is confusing.

what I mean is in this part :

func pickerView(pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int){

        labelPassedData.text = languagePicker[row]
}

in this part :

func numberOfComponentsInPickerView (pickerView : UIPickerView) -> Int{
    return 1
}

func pickerView(pickerView : UIPickerView , numberOfRowsInComponent component : Int) ->Int{
    return languagePicker.count
}

func pickerView(pickerView : UIPickerView, titleForRow row:Int, forComponent component : Int) -> String?
{
    return languagePicker[row]
}

func pickerView(pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int){

    labelPassedData.text = languagePicker[row]

    self.Insert(labelPassedData!.text!) // calling save lang function


    let Language = languageDB[0]
    dbshow!.text = Language.valueForKey("lang") as? String

    self.view.endEditing(true)
}

I get the value from core data but no change in visual picker view!

this is my code :

UPDATED Code

override func viewDidAppear(animated: Bool) {

fetch("Language")
let Language = languageDB[0]
let row_value : String = Language.valueForKey("lang") as! String

let row_num : Int

if(row_value == "فارسی"){

    row_num = 0
    self.pickerView.selectRow(row_num, inComponent: 0, animated: true)
    self.pickerView(self.pickerView, didSelectRow: row_num, inComponent: 0)

}else if(row_value == "English"){

    row_num = 1
    self.pickerView.selectRow(row_num, inComponent: 0, animated: true)
    self.pickerView(self.pickerView, didSelectRow: row_num, inComponent: 0)

}else if(row_value == "العربية"){

    row_num = 2
    self.pickerView.selectRow(row_num, inComponent: 0, animated: true)
    self.pickerView(self.pickerView, didSelectRow: row_num, inComponent: 0)
}

self.pickerView.reloadComponent(0)

}

Answer 1

I fixed the problem, it was related to declaring picker view datasource and delegate this part fixed my problem :

override func viewDidLoad() {
    super.viewDidLoad()

    self.pickerView.dataSource = self
    self.pickerView.delegate = self
}