发送信息到另一个视图控制器

Question

我在git集线器上发现了一个条形码扫描器项目，我将其合并到我的应用程序link中。我正在使用Google图书API来获取有关我扫描的图书的信息。

func getBookInfo(isbn: String) { 
    guard let url = URL(string: "https://www.googleapis.com/books/v1/volumes?q=isbn13:\(isbn)") else { 
     print("the url is not valid") 
     return 
    } 
    URLSession.shared.dataTask(with: url, completionHandler: {data, response, error -> Void in 
     guard error == nil else { 
      print(response) 
      print(error!.localizedDescription) 
      return 
     } 
     guard let data = data else { 
      print("no error but no data") 
      print(response) 
      return 
     } 
     guard let jsonResult = try? JSONSerialization.jsonObject(with: data, options: []) else { 
      print("the JSON is not valid") 
      return 
     } 
     if let arrayOfTitles = (jsonResult as AnyObject).value(forKeyPath: "items.volumeInfo.title") as? [String] { 
      self.BookName.text = "\(arrayOfTitles[0])" 
      print(self.BookName.text!) 
     } 
     if let arrayOfAuthors = (jsonResult as AnyObject).value(forKeyPath: "items.volumeInfo.authors") as? [[String]] { 
      self.Author.text = "\((arrayOfAuthors[0])[0])" 
      print(self.Author.text!) 
     } 
     if let arrayOfCategories = (jsonResult as AnyObject).value(forKeyPath: "items.volumeInfo.categories") as? [[String]] { 
      self.Category.text = "\((arrayOfCategories[0])[0])" 
      print(self.Category.text!) 
     } 
     if let arrayOfISBN13 = (jsonResult as AnyObject).value(forKeyPath: "items.volumeInfo.industryIdentifiers.identifier") as? [[String]] { 
      self.ISBN13.text = "\((arrayOfISBN13[0])[0])" 
      print(self.ISBN13.text!) 
     } 
     if let arrayOfISBN10 = (jsonResult as AnyObject).value(forKeyPath: "items.volumeInfo.industryIdentifiers.identifier") as? [[String]] { 
      self.ISBN10.text = "\((arrayOfISBN10[0])[1])" 
      print(self.ISBN10.text!) 
     } 
     if let arrayOfFormat = (jsonResult as AnyObject).value(forKeyPath: "items.volumeInfo.printType") as? [String] { 
      self.CoverType.text = "\(arrayOfFormat[0])" 
      print(self.CoverType.text!) 
     } 

    }).resume() 
} 

后，我扫描书籍，并已收到的信息，我想辞退具有条形码扫描仪，并在显示视图控制器视图控制器，我想显示我的书的信息只是扫描。

extension MultipleImageViewController: BarcodeScannerCodeDelegate { 

    func barcodeScanner(_ controller: BarcodeScannerController, didCaptureCode code: String, type: String) { 


     if code.isEmpty { 

      let delayTime = DispatchTime.now() + Double(Int64(6 * Double(NSEC_PER_SEC)))/Double(NSEC_PER_SEC) 
      DispatchQueue.main.asyncAfter(deadline: delayTime) { 
       controller.resetWithError() 

      } 

     } 
     else{ 

      getBookInfo(isbn: code) 


      let delayTime = DispatchTime.now() + Double(Int64(6 * Double(NSEC_PER_SEC)))/Double(NSEC_PER_SEC) 
      DispatchQueue.main.asyncAfter(deadline: delayTime) { 
       controller.dismiss(animated: true, completion: nil) 

      } 
     } 

    } 
} 

然而，当条形码扫描器视图控制器被驳回，我不得不退出程序，然后再回来到应用程序，以便为我的信息，在这我想它的视图控制器来显示。不用离开应用程序并返回来自条形码扫描器的信息不会显示在所需的视图控制器中。

Answer 1

您的用户界面没有更新，因为当视图控制器已被加载时，该视图控制器返回时，未调用方法viewDidLoad。相反，当你关闭子视图控制器时，为父项创建一个委托，该委托会被调用。有点像这样：

class ParentViewController: UIViewController, BarcodeDelegate { 
    func presentChildViewController() { 
     let childViewController = ChildViewController() 
     childViewController.delegate = self 
     present(childViewController, animated: true, completion: nil) 
    } 

    func dismissedChildViewController(code: String) { 
     // update UI 
    } 
} 

class ChildViewController: UIViewController { 
    var delegate: BarcodeDelegate? 

    func dismiss() { 
     delegate.dismissedChildViewController(code: getCode()) 
     dismiss(animated: true, completion: nil) 
    } 
} 

protocol BarcodeDelegate { 
    func dismissedChildViewController(code: String) 
} 

很难真正理解问题是什么，所以这可能是也可能不是你要找的。