如何在快速弹出视图控制器后传递数据

我正在制作一个关于书籍的应用程序。 在应用程序中， 我想让应用程序通过获取 ISBN（条形码）自动填充图书信息

views https://i.stack.imgur.com/ohz2S.png

有2个班。 一个是“UploadMain”，另一个是“ScanView”

我可以通过扫描获取ISBN， 但我在将数据从 ScanView 传递到 UploadMain 时遇到问题。

在 ScanView 中，我使用了如下所示的可选绑定

if let UploadVC = self.storyboard?.instantiateViewControllerWithIdentifier("UploadMain") as? UploadMain {
     UploadVC.ISBNstring = self.detectionString!
}

UploadMain类的代码

override func viewDidLoad(){
    super.viewDidLoad()
    ISBN.delegate = self

}

override func viewWillAppear(animated: Bool){
    ISBN.text = ISBNstring
}

我不知道我的代码有什么问题。

完整代码上传主

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)
}
}

扫描视图类

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)

}

}

In the ScanView您正在创建的新实例UploadMain，这在窗口层次结构中不可用，因此数据不可用于UploadMain。为了解决您的问题，您需要创建一个protocol并将该协议的委托传递给ScanView。所以创建一个protocol像这样。

protocol IsbnDelegate {
    func passData(isbnStr: String)
}

现在继承这个协议UploadMain并重写它的方法passData in the UploadMain像下面这样

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
     }
}

之后创建一个delegate对象在ScanView，更改您的代码ScanView像这样

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)

}

}

有关更多详细信息protcol点击此链接

1) 苹果文档 https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Protocols.html
2) 教程1 http://www.tutorialspoint.com/swift/swift_protocols.htm
3) 教程2 http://codewithchris.com/learn-swift-from-objective-c-part3/

希望对你有帮助。