CODEWITHSUNDEEP
swiftdelegatesswift-protocols
squarehippo10
squarehippo10

Reputation: 1945

Swift - Delegate function not returning value

VC-A is embedded in a nav controller and has a button going to VC-B via a popover segue. VC-B has a table view with a few font names. When I select a font name, VC-B closes and, using delegate/protocol, VC-A should get the selected name. It does not. I found that if I set a breakpoint at the end of didSelectRowAt, delegate is nil for some reason.

VC-A

class ViewController: UIViewController, FontDelegate {
    @IBOutlet weak var infoLabel: UILabel!
    let fontTable = FontTableTableViewController()

    override func viewDidLoad() {
        super.viewDidLoad()
        fontTable.delegate = self
    }
    
    func getFontName(data: String) {
        infoLabel.text = data
    }
}

VC-B

protocol FontDelegate {
    func getFontName(data: String)
}
    
class FontTableTableViewController: UITableViewController {

   let fontArray = ["Helvetica", "Arial", "Monaco"]
   var delegate: FontDelegate?

   // MARK: - Table view functions go here...

   override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
      let font = fontArray[indexPath.row]
      self.delegate?.getFontName(data: font)
      self.dismiss(animated: true, completion: nil)
   }
}

This shows the storyboard connection from the button in VC-A to VC-B.

enter image description here

Upvotes: 1

Views: 460

Answers (2)

MacUserT
MacUserT

Reputation: 1953

This is not the way how to return a variable in a navigation controller Environment. I would like to suggest you use an unwind segue. Your code would then look like:

VC A

class ViewController: UIViewController {

    var selectedFontName = ""
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
    }

    @IBAction func returnSelectedFont(sender: UIStoryboardSegue) {
        print(selectedFontName)
    }

}

The IBAction in VC A ist the method too which the tableview returns to if you use an unwind segue.

Your tableview controller then looks like this: VC B

import UIKit

class FontTableTableViewController: UITableViewController {

    var selectedFont = ""
    let fontArray = ["Helvetica", "Arial", "Monaco"]
    @IBOutlet var fontTable: UITableView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        fontTable.dataSource = self
        fontTable.delegate = self
    }

    // MARK: - Table view data source
    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        // #warning Incomplete implementation, return the number of rows
        return fontArray.count
    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "FontTable", for: indexPath) as! FontCell

        cell.fontName.text = fontArray[indexPath.row]

        return cell
    }
    
    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        selectedFont = fontArray[indexPath.row]
        performSegue(withIdentifier: "Return Fontname", sender: nil)
    }
    
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if let returnVC = segue.destination as? ViewController {
            returnVC.selectedFontName = selectedFont
        }
    }
}

To be able to get the return segue working you have to select the tableview cell and control drag it to the exit icon in the tableview controller. See therefore the picture.

After that you select the unwind segue and give it an identifier, to be used in VC B. See the code:

Make an unwind segue

Give the unwind segue an identifier

This should work perfectly.

Upvotes: 0

Amr
Amr

Reputation: 290

Instead of linking Pick your font button to the other controller, I would suggest you creating an IBAction of the button to trigger the following code whenever pressed:

let storyBoard = UIStoryboard(name: "Main", bundle: nil)
guard let vc = storyBoard.instantiateViewController(withIdentifier: "FontScreen") as? FontTableTableViewController else {return}
vc.delegate = self
vc.modalPresentationStyle = .fullScreen
self.navigationController?.pushViewController(vc, animated: true)

but for this to work you will need to go to the identity inspector of your FontTableTableViewController and from there you can name your controller in storyboardID field in Identity section as FontScreen.

Upvotes: 1

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