How to pass data in selected cell to another view controller?

Question

The piece of code below prints the content of whichever cell is clicked on in my TableView.

override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath)  {
    print(self.cell[indexPath.row])
}

I want to use the result that is printed in a label on another ViewController.

How do I get the string value from the function and then use it on on the other view? My thought is to use a global variable but I need to get the string value out first.

Do you want to display another view controller from the `didSelectRowAt` method? — rmaddy, Dec 03 '18 at 15:32
Possible duplicate of [Passing Data between View Controllers](https://stackoverflow.com/questions/5210535/passing-data-between-view-controllers) — Tamás Sengel, Dec 04 '18 at 09:41

Agisight · Accepted Answer · 2018-12-03T17:59:56.993

For example, You can use simple organization of a singleton of another ViewController (SecondScreen) with var main (in case, as usual, when SecondScreen inited via a Storyboard):

class SecondScreen : UIViewController {
    // 1. add this var
    static var main : SecondScreen? = nil

    // 2. Your some UI element
    @IBOutlet weak var textButton: UIButton!

    // 3. add this method
    func updateUI(string : String) {
        textButton.setTitle(string, for: .normal)
    }

    // 4. setting a var
    override func viewDidLoad() {
        if SecondScreen.main == nil {
            SecondScreen.main = self
        }
    }

    // ... another your and standard methods
}

And you can update your SecondScreen like this:

    let v = SecondScreen.main
    v?.updateUI(string: "yourString")

Also I recommend you to call method async:

DispatchQueue.main.async {
    SecondScreen.main?.updateUI(withString : string)
}

I suggest you to learn more about singletons...

Agisight · Answer 2 · 2018-12-03T18:01:22.580

0

At first, when you create a tableView, you have to collect data (string here) of cells in an array or another data collection. And you can get a needed data (strings) with indexPath variable in the method didSelectRowAt. And you can pass the string to another ViewController (let use SecondViewController) with several ways.

Here is an example:

// declaration an array of your strings
var array : [String] = ["First", "Second", "Third", ...]
...
// getting a string from method:
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath)  {
let string = array[indexPath.row]
print(string)
// next, for example, you need to pass the string to a singleton SecondViewController with static var **main**:
SecondViewController.main?.neededString = string
}

Don't forget update in async DispatchQueue:

DispatchQueue.main.async {
    SecondViewController.main?.updateUI(withString : string)
}

edited Dec 03 '18 at 18:01

answered Dec 03 '18 at 15:35

Agisight

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Thanks! that is working however I have to go to another page and then back before the second view controller updates. How would I force the second view controller to update in real time – wades Dec 03 '18 at 15:54
Try this ways: 1) You have to have an instance of second ViewController in some variable (Second VC can be a controller of subview or superview). And you can call a method of second VC, where you can change it's UI. 2) If you haven't an instance, you can init second VC with your string. – Agisight Dec 03 '18 at 16:13
the second view is actually an external monitor, the idea is that when a cell is clicked it displays the value of the cell in a label on the external monitor. I am very new to swift but i basically just need to refresh the external view. is that right? – wades Dec 03 '18 at 16:24
You can learn and use a variety of techniques: 1. a singleton, 2. the Notification Center and wait for updates, 3. use a delegates and protocols' methods, 4. use a blocks, 5. use a timer and listening the UserDefaults (crazy, but works). Some ways are described here: [link](https://stackoverflow.com/questions/5210535/passing-data-between-view-controllers?rq=1) – Agisight Dec 03 '18 at 16:42
I get an error saying SecondScreen has no member 'main' – wades Dec 03 '18 at 16:49
Yes, you need to organize a singleton class. – Agisight Dec 03 '18 at 17:07

How to pass data in selected cell to another view controller?

2 Answers2