Swift: pass string value from VC2 to VC1 on dismissViewControllerAnimated - ios

Question

first time asking after learning many useful things here!
I have a VC1 with a button and label.
The button is coded to present VC2 programmatically (without segue in IB).
VC2 has a tableview with the cells containing string values.
When I click on the cell in VC2, I am trying to get the string value of the selected cell and pass it back to the label.text in VC1.
First ViewController code:
class VC1: UIViewController {
... ...
#IBOutlet weak var LabelText: UILabel!
var passedString = "Example"
override func viewWillAppear(animated: Bool) {
LabelText.text = "\(passedString)"
}
#IBAction func chooseLabelTextBtnPressed(sender: AnyObject) {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc = storyboard.instantiateViewControllerWithIdentifier("VC2") as! VC2
self.presentViewController(vc, animated: true, completion: nil)
}
SecondViewController code:
class VC2: UIViewController, UITableViewDelegate, UITableViewDataSource {
... ...
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
// Get Cell Label
let indexPath = tableView.indexPathForSelectedRow;
let currentCell = tableView.cellForRowAtIndexPath(indexPath!) as! VC2_tableViewCell!;
let valueToPass = currentCell.IBOutletLbl.text
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let viewController = storyboard.instantiateViewControllerWithIdentifier("VC1") as! VC1
viewController.passedString = valueToPass!
//self.presentViewController(viewController, animated: true , completion: nil)
self.dismissViewControllerAnimated(true, completion: nil)
}
I hoped func viewWillAppear() in VC1 would update the String value of the label when VC2 is dismissed, but it doesn't.
I cannot use presentViewController from VC2 to VC1, because it might open again the VC1 instead of going back, and then other variables in VC1 would be inaccessible.
Help me! Thanks!

Answer 1

You should pass a delegate from VC1 to VC2 and then just call a delegate method for the update.
Send a reference here to VC2.
#IBAction func chooseLabelTextBtnPressed(sender: AnyObject) {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc = storyboard.instantiateViewControllerWithIdentifier("VC2") as! VC2
vc.delegate = self
self.presentViewController(vc, animated: true, completion: nil)
}
And before calling self.dismissViewControllerAnimated(true, completion: nil) in VC2 just call delegate.someMethod(someValue)
Also make sure your delegate is a weak reference.

Answer 2

When you do this:
let viewController = storyboard.instantiateViewControllerWithIdentifier("VC1") as! VC1
It creates a new instance of VC1 and doesn't actually reference the VC1 that presented VC2.
Instead you should add delegation between VC1 & VC2 to pass data around.