在没有互联网时，防止jsonserialization崩溃的最佳方法

Question

好吧，所以我找到了一些非常相似的问题的答案，但大多数人建议使用if语句或try/catch块，而我的代码都具有两者。我正在打电话给我的Web服务，该服务返回JSON，我使用JsonSerialization将其拉出以解析。由于标题暗示我的应用程序在没有互联网时会崩溃和燃烧，我希望有人能告诉我最好的解决这个问题的方法。我将在下面放置我的方法：

func getCategories() {
    activityIndicator?.startAnimating()
    tableView.isUserInteractionEnabled = false
    categoryArray = []
    let configuration = URLSessionConfiguration.default
    configuration.requestCachePolicy = NSURLRequest.CachePolicy.reloadIgnoringLocalCacheData
    let getQuizTitlesURL = URL(string: "https://myservice.com/my/directory/selectcategories.php")
    URLSession.shared.dataTask(with: getQuizTitlesURL! as URL, completionHandler: {(data, response, error) in
        do{
            if let parsedData = try JSONSerialization.jsonObject(with: data!, options: .allowFragments) as? NSArray {
                var name:String
                var categoryId:Int
                var quizCount:Int
                for index in 0...parsedData.count-1 {
                    let aObject = parsedData[index] as! [String : AnyObject]
                    name = (aObject["Name"] as? String)!
                    quizCount = Int(aObject["Count"] as! String)!
                    categoryId = (Int((aObject["ID"] as? String)!)!)
                    let category:Category = Category(name: name, quizCount: quizCount, categoryId: categoryId)
                    self.categoryArray.append(category)
                }
            }
            if let HTTPResponse = response as? HTTPURLResponse {
                print(HTTPResponse)
                let statusCode = HTTPResponse.statusCode
                if statusCode == 200 {
                    print("Success")
                }
            }
        }catch let error as NSError {
            print(error)
        }
        DispatchQueue.main.async {
            self.tableView.reloadData()
            self.activityIndicator?.stopAnimating()
            self.tableView.isUserInteractionEnabled = true
        }
    }).resume()
}

Answer 1

不要使用武力解开。

guard let data = data else { 
    // no data
    return
}
do {
    if let parsedData = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as? NSArray {
. . .

，正如@Joaofs所说，请在请求之前检查网络可用性。即使您检查此问题，请求响应期间的一切都可能。就像在请求之后刚断开网络一样。

Answer 2

我个人使用可及性，我在拨打电话之前检查连接是否可用

var reachability = Reachability()! // I declare this in the appDelegate as global variable
func getCategories() {
  if reachability.isReachable {
    // your code 
  } else {
  let alertViewController  = UIAlertController(title: "No Connection" , message: "There is something wrong with your internet Connection. Please check and try again", preferredStyle: .alert)
  let okAction = UIAlertAction(title: okTitle, style: .default) { (uialertAction) in
        alertViewController.dismiss(animated: true, completion: nil)
    }
    alertViewController.addAction(okAction)
  self.present(alertViewController, animated: true, completion: nil)
  }
}

Answer 3

如果没有网络，我不会尝试进行API调用。

另一方面，您应该确保在尝试序列化有效载荷之前获得HTTP状态代码，指示成功的响应。

Answer 4

制作一个新的Swift文件(可可类(，然后添加名称ressability.swift。在此文件中添加此代码：

import UIKit
import SystemConfiguration
protocol Utilities {
}
extension NSObject:Utilities{

enum ReachabilityStatus {
    case notReachable
    case reachableViaWWAN
    case reachableViaWiFi
}
var currentReachabilityStatus: ReachabilityStatus {
    var zeroAddress = sockaddr_in()
    zeroAddress.sin_len = UInt8(MemoryLayout<sockaddr_in>.size)
    zeroAddress.sin_family = sa_family_t(AF_INET)
    guard let defaultRouteReachability = withUnsafePointer(to: &zeroAddress, {
        $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
            SCNetworkReachabilityCreateWithAddress(nil,$0)
        }
    }) else {
        return .notReachable
    }
    var flags: SCNetworkReachabilityFlags = []
    if !SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags) {
        return .notReachable
    }
    if flags.contains(.reachable) == false {
        // The target host is not reachable.
        return .notReachable
    }
    else if flags.contains(.isWWAN) == true {
        // WWAN connections are OK if the calling application is using the CFNetwork APIs.
        return .reachableViaWWAN
    }
    else if flags.contains(.connectionRequired) == false {
        // If the target host is reachable and no connection is required then we'll assume that you're on Wi-Fi...
        return .reachableViaWiFi
    }
    else if (flags.contains(.connectionOnDemand) == true || flags.contains(.connectionOnTraffic) == true) && flags.contains(.interventionRequired) == false {
        // The connection is on-demand (or on-traffic) if the calling application is using the CFSocketStream or higher APIs and no [user] intervention is needed
        return .reachableViaWiFi
    }
    else {
        return .notReachable
    }
}
}

现在要实现您要实施网络服务和这样的东西的地方。

func checkReachability(){
    if (currentReachabilityStatus == .reachableViaWiFi) ||  (currentReachabilityStatus == .reachableViaWWAN) {
        // if wifi-connection or mobile-network-connection
        // YOUR_CODE
    } else {
        print("There is no internet connection")
        // make an alert to go to settings and enable mobile data/wifi.
        let alertController = UIAlertController (title: "Connectivity error!", message: "Go to Settings -> Enable Wi-Fi/Mobile Data", preferredStyle: .alert)
        let settingsAction = UIAlertAction(title: "Settings", style: .default) { (_) -> Void in
            guard let settingsUrl = URL(string: "App-Prefs:root") else {
                return
            }
            if UIApplication.shared.canOpenURL(settingsUrl) {
                UIApplication.shared.open(settingsUrl, completionHandler: { (success) in
                    print("Settings opened: (success)") // Prints true
                })
            }
        }
        alertController.addAction(settingsAction)
        present(alertController, animated: true, completion: nil)
    }
}

好吧，不要感谢我。祝你好运！！！！：D