CODEWITHSUNDEEP
iosswiftuiviewcontrollerdelegatesprotocols
Pippo
Pippo

Reputation: 1473

Get the correct Instance of ViewController for use with delegate function

I am trying to create a delegate function to reload a collection view in a different view controller on an event.

To this end i have defined a protocol, set the delegate in the class, and a simple delegate function.

protocol ReloadCollectionDelegate: class {
    func reloadCollectionViewFromDelegate()
}


class JourneyViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate, UITabBarControllerDelegate, UIScrollViewDelegate, ReloadCollectionDelegate {

    // delegate function from downloadCollectionController to relaod collection
    func reloadCollectionViewFromDelegate() {
        // simply call the reload function
        reloadCollection()
    }

And in my class that will be calling the above function:

// define the delegate for use
weak var reloadJourneyDelegate: ReloadCollectionDelegate?

// reload the collection view in JourneyViewController
let JVC = self.viewController.storyboard!.instantiateViewController(withIdentifier: "JourneyViewController") as! JourneyViewController
self.reloadJourneyDelegate = JVC
self.reloadJourneyDelegate?.reloadCollectionViewFromDelegate()

print(JVC):

JourneyViewController: 0x7fc7f7c55bf0

print(self) - from JourneyViewController (viewDidLoad):

JourneyViewController: 0x7fc7f7e2db10

So i am getting different instances of the same view controller.

How do i define this so i have the correct instance and can modify the UI?

Thanks

Upvotes: 1

Views: 686

Answers (2)

llamacorn
llamacorn

Reputation: 551

this worked for me where as the above answer did not:

let JCV = UIStoryboard(name: "Main", bundle: nil)
   .instantiateViewControllerWithIdentifier("JourneyViewController") as! JourneyViewController

The import part is that you have to add a storyboard ID in the identity inspector.

Upvotes: 0

Kawin P.
Kawin P.

Reputation: 188

This line creates a new instance of JourneyViewController

self.viewController.storyboard!.instantiateViewController(withIdentifier: "JourneyViewController") as! JourneyViewController

You must have a way to refer back to the original instance of JourneyViewController. Either by having a property that points to it or if both view controllers are in a hierarchy such that JourneyViewController is the parent of another view controller:

class ViewControllerA: UIViewController {
    override viewDidLoad() {
        let button = UIButton(frame: CGRect(x: self.view.bounds.width/2, y: 400, width: 50, height: 50))
        button.backgroundColor = UIColor.black
        button.addTarget(self, action: #selector(buttonPressed), for: .touchUpInside)
        self.view.addSubview(button) 
    }

    func buttonPressed() {
        let journey = self.parent as! JourneyViewController
        journey.reloadCollection()
    }
}

Upvotes: 1

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