If statement that performs segue with UIPicker

I am building an app where at a certain question I am able to use a UIPicker to go back to go back to previous questions, however I either get an error or nothing happens when attempting to use the app.

Also, all of my pages Storyboard ID is the name I am calling them for the segue.

I have tried using a switch statement but I get too many errors so I have decided that if statements might go better.

Old Switch Statement:

    public func textFieldDidEndEditing(_ textField: UITextField) {

    let row = picker.selectedRow(inComponent: 0)

    switch (row) {

    case 0: storyboard?.instantiateViewController(withIdentifier: "Q1") as? Q1; performSegue(withIdentifier: "Q1", sender: self)
    break;
    case 1: storyboard?.instantiateViewController(withIdentifier: "Q2") as? Q2; performSegue(withIdentifier: "Q2", sender: self)
    break;
    case 2: storyboard?.instantiateViewController(withIdentifier: "Q3") as? Q3; performSegue(withIdentifier: "Q3", sender: self)
    break;
    case 3: storyboard?.instantiateViewController(withIdentifier: "Q4") as? Q4; performSegue(withIdentifier: "Q4", sender: self)
    break;
    case 4: storyboard?.instantiateViewController(withIdentifier: "Q5") as? Q5; performSegue(withIdentifier: "Q5", sender: self)
    break;
    case 5: storyboard?.instantiateViewController(withIdentifier: "Q6") as? Q6; performSegue(withIdentifier: "Q6", sender: self)
    break;
    default: break;
}
}

The error I get is 'Use of undeclared type "Q1"'

I am trying to do something along the lines of,

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, 
inComponent component: Int) {
        DiffQuestion.text = data[row]

        if (data == "Q1") {
        storyboard?.instantiateViewController(withIdentifier: "Q1") as? Q1; 
    performSegue(withIdentifier: "Q1", sender: self)
       }
    }

Current error is on my if-statement "Binary operator '==' cannot be applied to operands of type '[String]' and 'String'" I know I probably structured it wrong, I'm still very new to all of this.