Swift：未知錯誤 - 意外地發現零，同時展開一個可選值

Question

我知道這是一個常見的錯誤，人們在這裏發佈，但我找不到與我在做什麼相匹配的帖子，即使它從根本上相同。我對Swift很陌生，只是試圖找到我的方式，謝謝。

我第一次打開我的應用程序，一個從MYSQL數據庫讀取的博客閱讀器應用程序，它可以按照預期工作，我可以關注我選擇和取消關注的博客。當我關注博客/單元格時，它會使用KeyArchiver保存到用戶默認值，但是當我雙擊主頁按鈕以從內存中清除應用程序並重新打開該應用程序時，它會崩潰。

蹊蹺的事情在我的loadUserDefaults因爲我設置斷點和崩潰，在這條線self.followedIdentifiers = Set(UserDefaults.standard.stringArray(forKey: "followedID")!)

我知道我有一個可選的，但爲什麼會崩潰/回來了零，如果我有saveUserDefaults救了它。它不是儲蓄嗎？或者我沒有正確加載它？

的錯誤是這樣

fatal error: unexpectedly found nil while unwrapping an Optional value

代碼：這是MainController.swift

var mainArray = [Blog]() 
var followedArray = [Blog]() 
var filteredArray = [Blog]() 
var followedIdentifiers = Set<String>() 

override func viewDidLoad() { 
    super.viewDidLoad() 

    // Receiving Data from Server 
    retrieveDataFromServer() 

    // NSCoding - Unarchiving Data (followedID) 
    loadUserDefaults() 
} 

// NSCoding: Archiving UserDefaults 
func saveUserDefaults() { 

    // Saving to UserDefaults 
    let encodedData = NSKeyedArchiver.archivedData(withRootObject: self.followedIdentifiers) 
    UserDefaults.standard.setValue(encodedData, forKey: "followedID") 
    UserDefaults.standard.synchronize() 
} 

// NSCoding: Unarchiving UserDefaults 
func loadUserDefaults() { // --- Crash is Here --- 

    // Unarchiving Data 
    if let data = UserDefaults.standard.data(forKey: "followedID"), let myFollowedList = NSKeyedUnarchiver.unarchiveObject(with: data) as? Set<String> { 

     self.followedIdentifiers = myFollowedList 
     self.followedIdentifiers = Set(UserDefaults.standard.stringArray(forKey: "followedID")!) // CRASH 

    } else { 
     print("Error/ Empty: (Loading UserDefaults (followedID))") 
    } 
} 

// Retrieving Data from Server 
func retrieveDataFromServer() { 

    let getDataURL = "http://example.com/receiving.php" 
    let url: NSURL = NSURL(string: getDataURL)! 

    do { 
     let data: Data = try Data(contentsOf: url as URL) 
     let jsonArray = try JSONSerialization.jsonObject(with: data, options: .mutableContainers) as! NSMutableArray 

     // Clear the arrays 
     self.followedArray = [Blog]() 
     self.mainArray = [Blog]() 

     // Looping through jsonArray 
     for jsonObject in jsonArray { 

      if let blog = Blog(jsonObject:jsonObject as! [String : Any]) { 

       // Check if identifiers match 
       if followedIdentifiers.contains(blog.blogID) { 
        self.followedArray.append(blog) 
       } else { 
        self.mainArray.append(blog) 
       } 
      } 
     } 
    } catch { 
     print("Error: (Retrieving Data)") 
    } 
    myTableView.reloadData() 
} 

這是Blog.swift負責處理所有的博客對象和NSCoding

class Blog: NSObject, NSCoding { 

var blogName: String 
var blogStatus1: String 
var blogStatus2: String 
var blogURL: String 
var blogID: String 
var blogType: String 
var blogDate: String 
var blogPop: String 


private init (name: String,status1: String,status2: String,url: String,id: String,type: String,date: String,pop: String) { 
    blogName = name 
    blogStatus1 = status1 
    blogStatus2 = status2 
    blogURL = url 
    blogID = id 
    blogType = type 
    blogDate = date 
    blogPop = pop 
    super.init() 
} 

convenience init?(jsonObject: [String:Any]) { 

    guard let bID = jsonObject["id"] as? String, 
     let bName = jsonObject["blogName"] as? String, 
     let bStatus1 = jsonObject["blogStatus1"] as? String, 
     let bStatus2 = jsonObject["blogStatus2"] as? String, 
     let bURL = jsonObject["blogURL"] as? String, 
     let bType = jsonObject["blogType"] as? String, 
     let bDate = jsonObject["blogDate"] as? String, 
     let bPop = jsonObject["blogPop"] as? String 

     else { 
      print("Error: (Creating Blog Object)") 
      return nil 
    } 

    self.init(name: bName, status1: bStatus1, status2: bStatus2, url: bURL, id: bID, type: bType, date: bDate, pop: bPop) 

} 

convenience required init?(coder aDecoder: NSCoder) { 
    guard let blogName = aDecoder.decodeObject(forKey: "blogName") as? String, 
     let blogStatus1 = aDecoder.decodeObject(forKey: "blogStatus1") as? String, 
     let blogStatus2 = aDecoder.decodeObject(forKey: "blogStatus2") as? String, 
     let blogURL = aDecoder.decodeObject(forKey: "blogURL") as? String, 
     let blogID = aDecoder.decodeObject(forKey: "blogID") as? String, 
     let blogType = aDecoder.decodeObject(forKey: "blogType") as? String, 
     let blogDate = aDecoder.decodeObject(forKey: "blogDate") as? String, 
     let blogPop = aDecoder.decodeObject(forKey: "blogPop") as? String else { 
      print("Error: (Creating Blog Object)") 
      return nil 
    } 
    self.init(name: blogName, status1: blogStatus1, status2: blogStatus2, url: blogURL, id: blogID, type: blogType, date: blogDate, pop: blogPop) 
} 

func encode(with aCoder: NSCoder) { 
    aCoder.encode(blogName, forKey: "blogName") 
    aCoder.encode(blogStatus1, forKey: "blogStatus1") 
    aCoder.encode(blogStatus2, forKey: "blogStatus2") 
    aCoder.encode(blogURL, forKey: "blogURL") 
    aCoder.encode(blogID, forKey: "blogID") 
    aCoder.encode(blogType, forKey: "blogType") 
    aCoder.encode(blogDate, forKey: "blogDate") 
    aCoder.encode(blogPop, forKey: "blogPop") 
} 
} 

Answer 1

我以前File Manager保存我的歸檔陣列，這是最好的選擇，非常簡單簡單。使用Swift 3。感謝@GuyKogus，@ Paulw11 & @MartinR

用它來保存我的對象

NSKeyedArchiver.archiveRootObject(myObject, toFile: filePath) 

用於放置我的對象

if let myFollowedList = NSKeyedUnarchiver.unarchiveObject(withFile: filePath) as? Set<String> { 

    myObject = myFollowedList 
}