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Access the instance of a Viewcontroller from another in swift

I am trying to transfer data from the textfield of one View Controller to the label from another.

How can I call the View Controller instance from the code of the other View Controller? I'm working with storyboards thus I never created an instance of the View Controllers in the code? Are the instances automatically created? And what name do they have?

Thanks for your help!

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McLawrence Avatar asked Aug 08 '14 13:08

McLawrence


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1 Answers

1. If the view controller containing the textfield can call (with a segue) the view controller containing the label...

Add a new Cocoa Touch class file in your project, name it FirstViewController and set the following code in it:

import UIKit  class FirstViewController: UIViewController {          @IBOutlet weak var textField: UITextField! // FIXME: link this to the UITextField in the Storyboard!!!          override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {         let controller = segue.destinationViewController as! SecondViewController         controller.text = textField.text     }      } 

Add a new Cocoa Touch class file in your project, name it SecondViewController and set the following code in it:

import UIKit  class SecondViewController: UIViewController {          var text: String?     @IBOutlet weak var label: UILabel! // FIXME: link this to the UILabel in the Storyboard!!!          override func viewDidLoad() {         super.viewDidLoad()                  label.text = text     }      } 

In the Storyboard, embed the first view controller in a UINavigationController. Link the first view controller to the second with a UIButton or a UIBarButtonItem. Set the name of the first view controller to FirstViewController and the name of the second view controller to SecondViewController. Create a UITextField in the first view controller. Create a UILabel in the second view controller. Link the textfield and the label to their respective declarations in FirstViewController and SecondViewController.


2. If the view controller containing the label can call (with a segue) the view controller containing the textfield...

Here, this is a perfect protocol/delegate case. You may find a lot of stuff on StackOverflow dealing with this. However, here is a rough example.

Add a new Cocoa Touch class file in your project, name it FirstViewController and set the following code in it:

import UIKit  class FirstViewController: UIViewController, DetailsDelegate {          @IBOutlet weak var label: UILabel! // FIXME: link this to the UILabel in the Storyboard          func updateLabel(withString string: String?) {         label.text = string     }          override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {         let controller = segue.destinationViewController as! SecondViewController         controller.delegate = self     }      } 

Add a new Cocoa/Cocoa Touch class file in your project, name it SecondViewController and set the following code in it:

import UIKit  protocol DetailsDelegate: class {     func updateLabel(withString string: String?) }  class SecondViewController: UIViewController {          weak var delegate: DetailsDelegate?     @IBOutlet weak var textField: UITextField! // FIXME: link this to the UITextField in the Storyboard          override func viewWillDisappear(animated: Bool) {         super.viewWillDisappear(animated)                  delegate?.updateLabel(withString: textField.text)     }  } 

In the Storyboard, embed the first view controller in a UINavigationController. Link the first view controller to the second with a UIButton or a UIBarButtonItem. Set the name of the first view controller to FirstViewController and the name of the second view controller to SecondViewController. Create a UILabel in the first view controller. Create a UITextField in the second view controller. Link the textfield and the label to their respective declarations in FirstViewController and SecondViewController.

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Imanou Petit Avatar answered Sep 25 '22 15:09

Imanou Petit