Trying to move a variable to from one class to another - ios

Question

I am currently trying to move one variable from one class to another. I am using the AVFramework to read QR Codes. The QR Code ultimately reads to a string variable and then the string variable reads to a label.text. I would like to use this exact same text within the textview of another class.
QRScannerController houses the QR code while HistoryViewis where I'd like to re-use the variable. The problem is that once I scan the QR code and move to the History view, it reads nothing. Here is what I have so far. Below is the QRScannerController
func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?){
if segue.destination .isKind(of:HistoryView.self){
let vc2 = segue.destination as! HistoryView
vc2.previousViewController = self
}
}
#IBOutlet var messageLabel:UILabel!
#IBOutlet var topbar: UIView!
#IBOutlet var segmentedControl: UISegmentedControl!
//#IBOutlet var textFacts: UITextView!
var captureSession:AVCaptureSession?
var videoPreviewLayer:AVCaptureVideoPreviewLayer?
var qrCodeFrameView:UIView?
let supportedCodeTypes = [AVMetadataObjectTypeUPCECode,
AVMetadataObjectTypeCode39Code,
AVMetadataObjectTypeCode39Mod43Code,
AVMetadataObjectTypeCode93Code,
AVMetadataObjectTypeCode128Code,
AVMetadataObjectTypeEAN8Code,
AVMetadataObjectTypeEAN13Code,
AVMetadataObjectTypeAztecCode,
AVMetadataObjectTypePDF417Code,
AVMetadataObjectTypeQRCode]
#IBAction func unwindToHomeScreen(segue: UIStoryboardSegue) {
dismiss(animated: true, completion: nil)
}
override func viewDidLoad() {
super.viewDidLoad()
// Get an instance of the AVCaptureDevice class to initialize a device object and provide the video as the media type parameter.
let captureDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
do {
// Get an instance of the AVCaptureDeviceInput class using the previous device object.
let input = try AVCaptureDeviceInput(device: captureDevice)
// Initialize the captureSession object.
captureSession = AVCaptureSession()
// Set the input device on the capture session.
captureSession?.addInput(input)
// Initialize a AVCaptureMetadataOutput object and set it as the output device to the capture session.
let captureMetadataOutput = AVCaptureMetadataOutput()
captureSession?.addOutput(captureMetadataOutput)
// Set delegate and use the default dispatch queue to execute the call back
captureMetadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
captureMetadataOutput.metadataObjectTypes = supportedCodeTypes
// Initialize the video preview layer and add it as a sublayer to the viewPreview view's layer.
videoPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
videoPreviewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill
videoPreviewLayer?.frame = view.layer.bounds
view.layer.addSublayer(videoPreviewLayer!)
// Start video capture.
captureSession?.startRunning()
// Move the message label and top bar to the front
view.bringSubview(toFront: messageLabel)
view.bringSubview(toFront: topbar)
// Initialize QR Code Frame to highlight the QR code
qrCodeFrameView = UIView()
if let qrCodeFrameView = qrCodeFrameView {
qrCodeFrameView.layer.borderColor = UIColor.green.cgColor
qrCodeFrameView.layer.borderWidth = 2
view.addSubview(qrCodeFrameView)
view.bringSubview(toFront: qrCodeFrameView)
}
} catch {
// If any error occurs, simply print it out and don't continue any more.
print(error)
return
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// MARK: - AVCaptureMetadataOutputObjectsDelegate Methods
public func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [Any]!, from connection: AVCaptureConnection!) {
// Check if the metadataObjects array is not nil and it contains at least one object.
if metadataObjects == nil || metadataObjects.count == 0 {
qrCodeFrameView?.frame = CGRect.zero
//messageLabel.text = "No QR/barcode is detected"
return
}
// Get the metadata object.
let metadataObj = metadataObjects[0] as! AVMetadataMachineReadableCodeObject
if supportedCodeTypes.contains(metadataObj.type) {
// If the found metadata is equal to the QR code metadata then update the status label's text and set the bounds
let barCodeObject = videoPreviewLayer?.transformedMetadataObject(for: metadataObj)
qrCodeFrameView?.frame = barCodeObject!.bounds
if metadataObj.stringValue != nil {
//captureSession?.stopRunning()
messageLabel.text = metadataObj.stringValue
messageLabel.text = messageLabel.text
//let vc: UINavigationController = storyboard?.instantiateViewController(withIdentifier: "View") as! UINavigationController
let vc3: UIViewController = storyboard!.instantiateViewController(withIdentifier: "View") //as! UIViewController
self.present(vc3, animated: true, completion: nil)
}
}
}
func transferViewControllerVariables() -> (UILabel){
return messageLabel
}
}
Here is the History View:
import UIKit
import AVFoundation
class HistoryView: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
#IBOutlet var textHistory:UITextView!
var previousViewController: QRScannerController?
#IBAction func unwindToHomeScreen(segue: UIStoryboardSegue) {
dismiss(animated: true, completion: nil)
}
#IBAction func toMaps(segue: UIStoryboardSegue) {
let vc3: UIViewController = storyboard!.instantiateViewController(withIdentifier: "front") //as! UIViewController
self.present(vc3, animated: true, completion: nil)
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
let messageLabel = previousViewController?.transferViewControllerVariables()
//print(messageLabel.text as Any)
textHistory.text = messageLabel?.text
}
// Do any additional setup after loading the view.
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}

Answer 1

I would propose you just pass the actual text to the next view controller instead of the whole previous view controller.
The general problem is though that the prepareForSegue function will never be called, as the HistoryView controller is not presented via a segue, but programmatically.
To pass data to the HistoryView controller programmatically do this in the captureOutput function in the QRScannerViewController:
let vc3: HistoryView = storyboard!.instantiateViewController(withIdentifier: "View") as! HistoryView
vc3.messagetext = metadataObj.stringValue
self.present(vc3, animated: true, completion: nil)
To add a new property in the history vc:
class HistoryView: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
var messageText: String?
}
Then you can remove the prepareForSegue function completely as it is not called anyway.

Answer 2

You should declare a messageLabel in HistoryView. when performing segue, assign the value and that's it.
class HistoryView: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
var messageLabel: String?
}
class QRCodeScanner: UIViewController {
func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?){
if segue.destination.isKind(of:HistoryView.self){
if let vc2 = segue.destination as? HistoryView {
vc2.messageLabel = self.messageLabel.text
}
}
}
}