向另一个视图控制器发送信息

Question

我在 git hub 上找到了一个条码扫描器项目，我将它并入了我的应用程序 link。我正在使用谷歌图书 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()
}

在我扫描书籍并收到信息后，我想关闭具有条形码扫描仪的视图控制器，并在出现的视图控制器中显示我刚刚扫描的书籍的信息。

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)

            }
        }

    }
}

但是，当条码扫描器视图控制器被关闭时，我必须退出应用程序，然后返回应用程序，以便我的信息在视图控制器中显示为我想要的。如果不离开应用程序并返回，我从条形码扫描仪收到的信息不会显示在所需的视图控制器中。

Answer 1

您的 UI 没有更新，因为在返回视图控制器时没有调用方法 viewDidLoad，因为它已经加载。相反，为父级创建一个委托，当您关闭子视图控制器时将调用该委托。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)
}

很难真正理解问题所在，因此这可能是也可能不是您要查找的内容。