Swift 3 Passing Data between view Controllers

debugcn Published at Dev

user5124826

I am attempting to pass data from one controller to the next. The code is as follows

First view controller:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    let parameters: Parameters = [
        "x": 2,
        "y": 2
    ]

    Alamofire.request(url, method: .post, parameters: parameters, encoding: URLEncoding.default).responseJSON { response in
        if((response.result.value) != nil) {
            let jsonVar: JSON = JSON(response.result.value ?? "success")
            let destViewController : JSONResult = segue.destination as! JSONResult
            let result = "\(jsonVar)"
            destViewController.textLabel = result
            print(result)
            //self.jsonDisplayError.text = "\(jsonVar)"
        } else {
            self.jsonDisplayError.text = "no response"
        }
    }
}

Second view controller:

@IBOutlet var jsonResult: UILabel!

var textLabel = String()

override func viewDidLoad() {
    jsonResult.text = textLabel
}

The result is being printed to the console correctly but it is not displaying in the label on the second view controller page.

Okan Kocyigit

I think the problem is sending data in async callback, you've two options here,

First Solution

Pass parameters to secondviewcontroller and make your API request on secondviewcontroller's viewdidload event.

class FirstViewController: UIViewController {
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        let parameters: Parameters = [
            "x": 2,
            "y": 2
        ]
        destViewController.parametrs = parameters
    }
}

And secondviewcontroller,

class SecondViewController: UIViewController {
    @IBOutlet var jsonResult: UILabel!

    var parameters: Parameters

    override func viewDidLoad() {
        Alamofire.request(url, method: .post, parameters: parameters, encoding: URLEncoding.default).responseJSON { response in
            if((response.result.value) != nil) {
                let jsonVar: JSON = JSON(response.result.value ?? "success")
                jsonResult.text = result
            } else {
                self.jsonDisplayError.text = "no response"
            }
        }
    }
}

Second Solution

Create a seque between two viewcontroller (not button click etc.), and performSegue manually when your async callback completed,

class FirstViewController: UIViewController {
    var result = ""
    @IBAction func buttonClick(sender: UIButton) {
        let parameters: Parameters = [
            "x": 2,
            "y": 2
        ]

        Alamofire.request(url, method: .post, parameters: parameters, encoding: URLEncoding.default).responseJSON { response in
            if((response.result.value) != nil) {
                let jsonVar: JSON = JSON(response.result.value ?? "success")
                self.result = "\(jsonVar)"
                self.performSegue(withIdentifier: "yourSegueIdentifier", sender: nil)
            } else {
                self.jsonDisplayError.text = "no response"
            }
        }
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        let destViewController : JSONResult = segue.destination as! JSONResult
        destViewController.textLabel = self.result
    }
}

Second view controller:

class SecondViewController: UIViewController {
    @IBOutlet var jsonResult: UILabel!

    var textLabel = String()

    override func viewDidLoad() {
        jsonResult.text = textLabel
    }
}

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