CODEWITHSUNDEEP
iosswiftxcodedelegates
Lucas
Lucas

Reputation: 766

why doesn't this code for passing data between controllers work?

I'm trying to understand delegates so I created this simple app to test it out, I just want to pass a string from the secondViewController to the MainViewController... I tried to follow all the steps but it seems there's something missing and I don't have a clue about what it might possibly be... here's my code..

main view controller

class mainController: UIViewController, sendDataDelegate {

    let label: UILabel = {
        let lab = UILabel()
        lab.text = "No data"
        lab.textAlignment = .center
        lab.translatesAutoresizingMaskIntoConstraints = false
        return lab
    }()

    let tapRecognizer = UITapGestureRecognizer()
    let secondVC = SecondViewController()


    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = UIColor.green


        //  assign delegate to self, not working...
        secondVC.delegate = self


        tapRecognizer.addTarget(self, action: #selector(goToSecondVC))
        view.addGestureRecognizer(tapRecognizer)
        view.addSubview(label)

        // label constraints..
        view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|[v0]|", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0":label]))
        view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|-200-[v0]", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0":label]))
    }

    @objc func goToSecondVC(){
           show(SecondViewController(), sender: nil)
    }

    func passData(str: String) {
        print(str)
        label.text = str

    }

}

and the second view controller plus protocol to send the data...

import UIKit


//protocol to pass the data..

protocol sendDataDelegate {
    func passData(str: String)
}



class SecondViewController: UIViewController {

    let tapRecog = UITapGestureRecognizer()

    let dataStr = "data passed"


    var delegate: sendDataDelegate?



    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = UIColor.red
        tapRecog.addTarget(self, action: #selector(goBack))
        view.addGestureRecognizer(tapRecog)

    }

    @objc func goBack(){

//        trying to pass data here..
        delegate?.passData(str: dataStr)

//        dismiss view...
        dismiss(animated: true, completion: nil)

    }

}

I'd like to point out I'm trying to learn everything by code, so no storyboards being used here.. how can I do this just by code?

thank you all in advance for the answers! have a great day)

Upvotes: 0

Views: 92

Answers (3)

Sergey
Sergey

Reputation: 682

This correction will solve your problem:

@objc func goToSecondVC(){
    show(secondVC, sender: nil)
}

Protocols are better to be named with a capital letter:

 protocol SendDataDelegate: AnyObject {
     func passData(str: String)
 }

And don't forget about weak delegate:

weak var delegate: SendDataDelegate?

Upvotes: 2

Moayad Al kouz
Moayad Al kouz

Reputation: 1392

change goToSecondVC() method as below: 

 @objc func goToSecondVC(){
        let vc = SecondViewController()
        vc.delegate = self
        show(vc, sender: nil)
 }

Upvotes: -1

Fogmeister
Fogmeister

Reputation: 77641

In your function goToSecondVC you are creating a brand new view controller and ignoring the property that you created.

Change it to use secondVC instead of SecondViewController().

Upvotes: 3

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