从另一个ViewController设置值文本字段

Question

i edited my question , because set textfield maybe can't be simple, need references so this is my code, but still have issue :

this code for TableViewController :

import UIKit

protocol PaymentSelectionDelegate{
func userDidSelectPayment(title: NSString?)
}

class PopPaymentTableViewController: UITableViewController {

    var delegate : PaymentSelectionDelegate!

    override func viewDidLoad() {
        super.viewDidLoad()

    }   

   override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath?) {

    self.dismissViewControllerAnimated(true){
        if self.delegate != nil{
            if let ip = indexPath{
                var payItem : PayMethod

                payItem = self.myList[ip.row] as! PayMethod

                var title = payItem.paymentName

               self.delegate.userDidSelectPayment(title)
               }
           }
       }
   }


}

and for code TransactionViewController :

 import UIKit

 class TransactionViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate, PaymentSelectionDelegate, UITextFieldDelegate, UIPopoverPresentationControllerDelegate{

 @IBOutlet var paymentTextField: UITextField!

 override func viewDidLoad() {
    super.viewDidLoad()
 }


    func resign(){

        paymentTextField.resignFirstResponder()
   } 

  func textFieldShouldBeginEditing(textField: UITextField) -> Bool {
       if (textField == paymentTextField){
        resign()

        performSegueWithIdentifier("seguePayment", sender: self)
       }
  }

  func adaptivePresentationStyleForPresentationController(controller: UIPresentationController) -> UIModalPresentationStyle {
    return .None
  }


  func userDidSelectPayment(title: NSString?) {
    paymentTextField.text = title as! String
  }

  override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

    if segue.identifier == "seguePayment"{

        var VC = segue.destinationViewController as! UINavigationController

        var controller  = VC.popoverPresentationController

        if controller != nil{
            controller?.delegate = self

            var paymentVC = PopPaymentTableViewController()
            paymentVC.delegate = self
        }
    }

}


}

this issue is: variable delegate in TableViewController like seems always nil, so cant set value

NB : sorry i edited totally my question, because so many answer say cant be set textfield just like that

Answer 1

The context of where your TransactionViewController is, is not completely clear, but you are instantiating a new ViewController. If you want to refer to an existing ViewController, this is not the instance you are using here. If you want to create a new one and show it after your didSelectRowAtIndexPath, you have to make sure, that the TextField is instantiated in the init-Method of your ViewController. As you are not instantiating it from a Storyboard, it seems that your TransactionViewController is created programmatically. Probably you are setting the TextField only in viewDidLoad or something else after the init().

Answer 2

You are trying to set text to paymentTextField which is still no initialized.

For this you have to set text to paymentTextField in viewDidLoad method in TransactionViewController .

remove transVC.paymentTextField.text = title from didSelectRowAtIndexPath

Add it in TransactionViewController 's viewDidLoad

override func viewDidLoad() {
    super.viewDidLoad()

   self.paymentTextField.text =  self.payName
}

Answer 3

It is not correct way to do that. You have not initialised text field and trying to set it's text. First initialise text field:

transVC.paymentTextField = UITextField()

Then try to do something.