How do I pass a scanned barcode ID from first view controller to second View Controller's UILabel? - swift

Question

This is the barcode scanning tutorial I used in my program, so that you have a lot more context when you read my code: Link
Here is what my program does so far: Essentially, when I scan an item's barcode with my phone, the UIAlert pops up with the barcode ID displayed and a button prompting the user to open the "Results" page. This is all fine and good, but how do I pass that same scanned barcode ID into a label on the Result's page? I have been stuck on this for 2 days now, even though it seems like such an easy task.
Any help is much appreciated <3
Here is my relevant code:
ProductCatalog.plist ->
Link to Image
Scanner_ViewController.swift (first View Controller) ->
import UIKit
import AVFoundation
class Scanner_ViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate, ScannerDelegate
{
private var scanner: Scanner?
override func viewDidLoad()
{
super.viewDidLoad()
self.scanner = Scanner(withDelegate: self)
guard let scanner = self.scanner else
{
return
}
scanner.requestCaptureSessionStartRunning()
}
override func didReceiveMemoryWarning()
{
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// Mark - AVFoundation delegate methods
public func metadataOutput(_ output: AVCaptureMetadataOutput,
didOutput metadataObjects: [AVMetadataObject],
from connection: AVCaptureConnection)
{
guard let scanner = self.scanner else
{
return
}
scanner.metadataOutput(output,
didOutput: metadataObjects,
from: connection)
}
// Mark - Scanner delegate methods
func cameraView() -> UIView
{
return self.view
}
func delegateViewController() -> UIViewController
{
return self
}
func scanCompleted(withCode code: String)
{
print(code)
showAlert_Success(withTitle: (code))
}
private func showAlert_Success(withTitle title: String)
{
let alertController = UIAlertController(title: title, message: "Product has been successfully scanned", preferredStyle: .alert)
// programatically segue to the next view controller when the UIAlert pops up
alertController.addAction(UIAlertAction(title:"Get Results", style: .default, handler:{ action in self.performSegue(withIdentifier: "toAnalysisPage", sender: self) }))
present(alertController, animated: true)
}
}
Scanner.Swift (accompanies Scanner_ViewController.swift)->
import Foundation
import UIKit
import AVFoundation
protocol ScannerDelegate: class
{
func cameraView() -> UIView
func delegateViewController() -> UIViewController
func scanCompleted(withCode code: String)
}
class Scanner: NSObject
{
public weak var delegate: ScannerDelegate?
private var captureSession : AVCaptureSession?
init(withDelegate delegate: ScannerDelegate)
{
self.delegate = delegate
super.init()
self.scannerSetup()
}
private func scannerSetup()
{
guard let captureSession = self.createCaptureSession()
else
{
return
}
self.captureSession = captureSession
guard let delegate = self.delegate
else
{
return
}
let cameraView = delegate.cameraView()
let previewLayer = self.createPreviewLayer(withCaptureSession: captureSession,
view: cameraView)
cameraView.layer.addSublayer(previewLayer)
}
private func createCaptureSession() -> AVCaptureSession?
{
do
{
let captureSession = AVCaptureSession()
guard let captureDevice = AVCaptureDevice.default(for: .video) else
{
return nil
}
let deviceInput = try AVCaptureDeviceInput(device: captureDevice)
let metaDataOutput = AVCaptureMetadataOutput()
// add device input
if captureSession.canAddInput(deviceInput) && captureSession.canAddOutput(metaDataOutput)
{
captureSession.addInput(deviceInput)
captureSession.addOutput(metaDataOutput)
guard let delegate = self.delegate,
let viewController = delegate.delegateViewController() as? AVCaptureMetadataOutputObjectsDelegate else
{
return nil
}
metaDataOutput.setMetadataObjectsDelegate(viewController,
queue: DispatchQueue.main)
metaDataOutput.metadataObjectTypes = self.metaObjectTypes()
return captureSession
}
}
catch
{
// handle error
}
return nil
}
private func createPreviewLayer(withCaptureSession captureSession: AVCaptureSession,
view: UIView) -> AVCaptureVideoPreviewLayer
{
let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
previewLayer.frame = view.layer.bounds
previewLayer.videoGravity = .resizeAspectFill
return previewLayer
}
private func metaObjectTypes() -> [AVMetadataObject.ObjectType]
{
return [.qr,
.code128,
.code39,
.code39Mod43,
.code93,
.ean13,
.ean8,
.interleaved2of5,
.itf14,
.pdf417,
.upce
]
}
public func metadataOutput(_ output: AVCaptureMetadataOutput,
didOutput metadataObjects: [AVMetadataObject],
from connection: AVCaptureConnection)
{
self.requestCaptureSessionStopRunning()
guard let metadataObject = metadataObjects.first,
let readableObject = metadataObject as? AVMetadataMachineReadableCodeObject,
let scannedValue = readableObject.stringValue,
let delegate = self.delegate
else
{
return
}
delegate.scanCompleted(withCode: scannedValue)
}
public func requestCaptureSessionStartRunning()
{
self.toggleCaptureSessionRunningState()
}
public func requestCaptureSessionStopRunning()
{
self.toggleCaptureSessionRunningState()
}
private func toggleCaptureSessionRunningState()
{
guard let captureSession = self.captureSession
else
{
return
}
if !captureSession.isRunning
{
captureSession.startRunning()
}
else
{
captureSession.stopRunning()
}
}
}
Analysis_ViewController.swift (second view controller) ->
Right now, the forKey: has been hard-coded to item ID 8710908501708 because I have no idea how to actually pass camera-scanned ID's into the second View Controller :/
import UIKit
class Analysis_ViewController: UIViewController
{
#IBOutlet weak var productTitle: UILabel!
func getData()
{
let path = Bundle.main.path(forResource:"ProductCatalog", ofType: "plist")
let dict:NSDictionary = NSDictionary(contentsOfFile: path!)!
if (dict.object(forKey: "8710908501708" as Any) != nil)
{
if let levelDict:[String : Any] = dict.object(forKey: "8710908501708" as Any) as? [String : Any]
{
// use a for loop to iterate through all the keys and values in side the "Levels" dictionary
for (key, value) in levelDict
{
// if we find a key named whatever we care about, we can print out the value
if (key == "name")
{
productTitle.text = (value as! String)
}
}
}
}
}
// listing the better options that are safer in comparison to the scanned product image
override func viewDidLoad()
{
super.viewDidLoad()
getData()
}
}

Answer 1

Do you have a variable to hold the scanned ID in your view controllers? If not, you can add var itemID: String? to both Scanner_ViewController and Analysis_ViewController.
Then in your func where you get the scanned code, you can set it to the variable.
func scanCompleted(withCode code: String) {
print(code)
itemID = code // Saves the scanned code to your var
showAlert_Success(withTitle: (code))
}
For passing data to another view controller via segue, you might want to look into this UIViewController method for segues: documentation here. This answer also might help.
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "toAnalysisPage" {
if let viewController = segue.destination as? Analysis_ViewController {
viewController.itemID = itemID
}
}
}