how to pass data after pop view controller in swift - ios

Question

I am making an app about book.
In the app,
i want to make the app auto-filling book info by getting ISBN(Barcode)
views
There is 2 classes.
one is 'UploadMain',the other is 'ScanView'
I can get ISBN by scanning,
but i have a problem to pass data from ScanView to UploadMain.
In ScanView i have used optional Binding like below
if let UploadVC = self.storyboard?.instantiateViewControllerWithIdentifier("UploadMain") as? UploadMain {
UploadVC.ISBNstring = self.detectionString!
}
Code for UploadMain Class
override func viewDidLoad(){
super.viewDidLoad()
ISBN.delegate = self
}
override func viewWillAppear(animated: Bool){
ISBN.text = ISBNstring
}
i don't know whats the problem my code.
Full Code of UploadMain
import UIKit
import Foundation
class UploadMain: UIViewController,UITextFieldDelegate {
var ISBNstring: String = ""
var TitleString: String = ""
var AuthorString: String = ""
var PubString: String = ""
var PriceSting: String = ""
#IBOutlet weak var ISBN: UITextField!
#IBOutlet weak var bookTitle: UITextField!
#IBOutlet weak var bookAuthor: UITextField!
#IBOutlet weak var bookPub: UITextField!
#IBOutlet weak var bookPrice: UITextField!
override func viewDidLoad(){
super.viewDidLoad()
ISBN.delegate = self
}
override func viewWillAppear(animated: Bool){
ISBN.text = ISBNstring
}
#IBAction func Upload(sender: AnyObject) {
dismissViewControllerAnimated(true, completion: nil)
}
}
ScanView class
import UIKit
import AVFoundation
import Foundation
class ScanView : UIViewController, AVCaptureMetadataOutputObjectsDelegate {
let session : AVCaptureSession = AVCaptureSession()
var previewLayer : AVCaptureVideoPreviewLayer!
var detectionString : String!
let apiKey : String = "---------dddddd"
override func viewDidLoad() {
super.viewDidLoad()
// For the sake of discussion this is the camera
let device = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
// Create a nilable NSError to hand off to the next method.
// Make sure to use the "var" keyword and not "let"
var error : NSError? = nil
var input: AVCaptureDeviceInput = AVCaptureDeviceInput()
do {
input = try AVCaptureDeviceInput(device: device) as AVCaptureDeviceInput
} catch let myJSONError {
print(myJSONError)
}
// If our input is not nil then add it to the session, otherwise we're kind of done!
if input != AVCaptureDeviceInput() {
session.addInput(input)
}
else {
// This is fine for a demo, do something real with this in your app. :)
print(error)
}
let output = AVCaptureMetadataOutput()
output.setMetadataObjectsDelegate(self, queue: dispatch_get_main_queue())
session.addOutput(output)
output.metadataObjectTypes = output.availableMetadataObjectTypes
previewLayer = AVCaptureVideoPreviewLayer(session: session)
previewLayer.frame = self.view.bounds
previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
self.view.layer.addSublayer(previewLayer)
// Start the scanner. You'll have to end it yourself later.
session.startRunning()
}
// This is called when we find a known barcode type with the camera.
func captureOutput(captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [AnyObject]!, fromConnection connection: AVCaptureConnection!) {
var highlightViewRect = CGRectZero
var barCodeObject : AVMetadataObject!
let barCodeTypes = [AVMetadataObjectTypeEAN13Code, AVMetadataObjectTypeEAN8Code]
// The scanner is capable of capturing multiple 2-dimensional barcodes in one scan.
for metadata in metadataObjects {
for barcodeType in barCodeTypes {
if metadata.type == barcodeType {
barCodeObject = self.previewLayer.transformedMetadataObjectForMetadataObject(metadata as! AVMetadataMachineReadableCodeObject)
highlightViewRect = barCodeObject.bounds
detectionString = (metadata as! AVMetadataMachineReadableCodeObject).stringValue
self.session.stopRunning()
self.alert(detectionString)
// Daum Book API 호출
let apiURI = NSURL(string: "https://apis.daum.net/search/book?apikey=\(apiKey)&q=\(detectionString)&searchType=isbn&output=json")
let apidata : NSData? = NSData(contentsOfURL: apiURI!)
NSLog("API Result = %#", NSString(data: apidata!, encoding: NSUTF8StringEncoding)!)
**if let UploadVC = self.storyboard?.instantiateViewControllerWithIdentifier("UploadMain") as? UploadMain {
UploadVC.ISBNstring = self.detectionString!
}**
break
}
}
}
print(detectionString)
self.navigationController?.popViewControllerAnimated(true)
}
func alert(Code: String){
let actionSheet:UIAlertController = UIAlertController(title: "Barcode", message: "\(Code)", preferredStyle: UIAlertControllerStyle.Alert)
// for alert add .Alert instead of .Action Sheet
// start copy
let firstAlertAction:UIAlertAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler:
{
(alertAction:UIAlertAction!) in
// action when pressed
self.session.startRunning()
})
actionSheet.addAction(firstAlertAction)
}
}

Answer 1

In the ScanView you are creating the new instance of UploadMain, that is not available in window hierarchy, So that data is not available to the UploadMain. To solve your problem you need to create one protocol and pass the delegate of that protocol to ScanView. So create one protocol like this.
protocol IsbnDelegate {
func passData(isbnStr: String)
}
Now inherit this protocol in UploadMain and override its method passData in the UploadMain like below
class UploadMain: UIViewController,UITextFieldDelegate,IsbnDelegate {
//your code
//Add this method
func passData(isbnStr: String) {
self.ISBN.text = isbnStr
}
//Also override prepareForSegue like this
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
let destVC = segue.destinationViewController as! ScanView
destVC.delegate = self
}
}
After that create one delegate object in ScanView, Change your code of ScanView like this
import UIKit
import AVFoundation
import Foundation
class ScanView : UIViewController, AVCaptureMetadataOutputObjectsDelegate {
let session : AVCaptureSession = AVCaptureSession()
var previewLayer : AVCaptureVideoPreviewLayer!
var detectionString : String!
let apiKey : String = "---------dddddd"
var delegate: IsbnDelegate?
override func viewDidLoad() {
super.viewDidLoad()
// For the sake of discussion this is the camera
let device = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
// Create a nilable NSError to hand off to the next method.
// Make sure to use the "var" keyword and not "let"
var error : NSError? = nil
var input: AVCaptureDeviceInput = AVCaptureDeviceInput()
do {
input = try AVCaptureDeviceInput(device: device) as AVCaptureDeviceInput
} catch let myJSONError {
print(myJSONError)
}
// If our input is not nil then add it to the session, otherwise we're kind of done!
if input != AVCaptureDeviceInput() {
session.addInput(input)
}
else {
// This is fine for a demo, do something real with this in your app. :)
print(error)
}
let output = AVCaptureMetadataOutput()
output.setMetadataObjectsDelegate(self, queue: dispatch_get_main_queue())
session.addOutput(output)
output.metadataObjectTypes = output.availableMetadataObjectTypes
previewLayer = AVCaptureVideoPreviewLayer(session: session)
previewLayer.frame = self.view.bounds
previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
self.view.layer.addSublayer(previewLayer)
// Start the scanner. You'll have to end it yourself later.
session.startRunning()
}
// This is called when we find a known barcode type with the camera.
func captureOutput(captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [AnyObject]!, fromConnection connection: AVCaptureConnection!) {
var highlightViewRect = CGRectZero
var barCodeObject : AVMetadataObject!
let barCodeTypes = [AVMetadataObjectTypeEAN13Code, AVMetadataObjectTypeEAN8Code]
// The scanner is capable of capturing multiple 2-dimensional barcodes in one scan.
for metadata in metadataObjects {
for barcodeType in barCodeTypes {
if metadata.type == barcodeType {
barCodeObject = self.previewLayer.transformedMetadataObjectForMetadataObject(metadata as! AVMetadataMachineReadableCodeObject)
highlightViewRect = barCodeObject.bounds
detectionString = (metadata as! AVMetadataMachineReadableCodeObject).stringValue
self.session.stopRunning()
self.alert(detectionString)
// Daum Book API 호출
let apiURI = NSURL(string: "https://apis.daum.net/search/book?apikey=\(apiKey)&q=\(detectionString)&searchType=isbn&output=json")
let apidata : NSData? = NSData(contentsOfURL: apiURI!)
NSLog("API Result = %#", NSString(data: apidata!, encoding: NSUTF8StringEncoding)!)
//Here We are passing the data of your ScanView to UploadMain
self.delegate.passData(self.detectionString!)
break
}
}
}
print(detectionString)
self.navigationController?.popViewControllerAnimated(true)
}
func alert(Code: String){
let actionSheet:UIAlertController = UIAlertController(title: "Barcode", message: "\(Code)", preferredStyle: UIAlertControllerStyle.Alert)
// for alert add .Alert instead of .Action Sheet
// start copy
let firstAlertAction:UIAlertAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler:
{
(alertAction:UIAlertAction!) in
// action when pressed
self.session.startRunning()
})
actionSheet.addAction(firstAlertAction)
}
}
For more detail about protcol follow this link
1) Apple Documentation
2) Tutorial 1
3) Tutorial 2
Hope this will help you.

Answer 2

To me it appears you are passing data back from the view controller.
When you call
if let UploadVC = self.storyboard?.instantiateViewControllerWithIdentifier("UploadMain") as? UploadMain {
UploadVC.ISBNstring = self.detectionString!
}
You are creating a new instance of that view controller, and it is successfully receiving the data (But you could never use it).
What you are wanting to do is send data
I could write it out for you, but theres actually some great tutorials
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